CA See combining ability.

cachectic adj. Affected by or relating to cachexia.

cachexia n. Weight loss, wasting of muscle, loss of appetite, and general debility that can occur during a chronic disease.

cacti See cactus.

cactiform adj. With succulent stems similar to Cactaceae.

cactoid adj. Resembling a cactus.

cactus n. (pl. cacti) A member of the family Cactaceae, having succulent stems and branches with scales or spines instead of leaves and found primarily in arid regions.

caducous (L. caducus: destined to fall, perishable) adj. Said of a plant part, such as a sepal, petal, or leaf, that falls off quickly or early. Cf. deciduous.

caeruleous See caeruleus.

caeruleus (L. cŠrulus: blue) adj. Sky blue. Also caeruleous.

caerulescent (L. cŠrulus: blue) adj. Bluish. Syn. Syn. coerulean.

caesious (L. cŠsius: somewhat green) adj. Light grey, bluish or glaucous blue. adj. Growing in tufts or clumps; matted.

caespitose (L. cespes, cespitis: tuft of turf) adj. Growing in dense tufts or clumps, in cushions or sods; matted. Also cespitose, caespitous.

caespitous See caespitose.

caffeic acid A phenol formed from cinnamic acid, more frequently occurs as an ester, as in chlorigenic acid.

caffeine n. A pseudoalkaloid.

calathide n. See capitulum.

calathiform (Gr. kalathos: basket; L. forma: shape) adj. Basket-shaped or cup-shaped.

calcar (Gr. calx, calcis: heel) n. (pl. calcaria) A spur or spurlike appendage.

calcarate (Gr. calx, calcis: heel) adj. Produced into or having a spur.

calcareous adj. Containing calcium or calcium carbonate (lime), as an alkaline soil.

calcareous ooze Partially decomposed organic matter mixed with a quantity of calcareous material on the bottom of some bodies of water.

calceiform See calceolate.

calceolate (L. calceolus, diminutive of calceus: shoe) adj. Shoe-shaped or slipper-shaped, as the labellum of some orchids.

calcicole (L. calx, calcis: lime) adj., n. A plant growing best on calcareous soil. A calcicole plant. Cf. basiphile. Also calciphile, calcicolous.

calcicolous See calcicole.

calcification n. A soil process where the surface soil is combined with calcium by the decomposition of plants, especially if a calcareous layer is formed. Cf. podzolization.

calcifuge (L. calx, calcis: lime; fuga: flight, escape) adj., n. A plant which avoids calcareous soil, not suited to calcareous; growing on base-poor or acidic substrates.

calcination n. Decomposition due to the loss of bound water and carbon dioxide.

calcine adj. Like a calyx, or belonging to the calyx.

calciphile See calciphilous.

calciphilous (L. calx, calcis: lime; Gr. phile˘: to like) adj. Lime-loving; a plant that must have lime or alkaline soil. Also calciphile, calcicole, calcicolous. Cf. basiphile.

calciphobe adj. A plant preferring alkaline soils; an acidophilous plant.

calcium carbonate A 'salt' used by many marine invertebrates, such as corals and echinoderms, and by protists, such as coccolithophorids, to construct their exoskeletons.

calcium oxalate Ca C2 H2 O4. The crystalline form is common in plant cells, either as druses, raphides, sand, or styloids.

Caledonian orogeny Major mountain-building episode which took place during the Lower Palaeozoic Era. The orogeny affected Greenland, Ireland, Scotland, and Scandinavia, and was associated with the closure of the Iapetus Ocean between the old continents of Laurentia, Gondwana, and Baltica.

calicate See calycate

caliciform (L. calyx: cup; forma: shape) adj. Cup-shaped.

calicle See calycle.

calicole adj. A plant living on chalky or limy soils.

calli n. Small outgrowths on the throat of the corolla of some plants, often acting as tactile guides for pollinators.

callose (L. callum: thick, hard skin) adj. Having thickened or hardened spots, as a leaf; having a callus. Syn. callous.

callosity (L. callum: thick, hard skin) n. A hardened or thickened area; the condition of being callous.

callous (L. callum: thick, hard skin) adj. Hardened or thickened; having a callus.

callus (L. callus, callum, hard skin) n. (pl. calluses) A hard protuberance or callosity; new tissue covering a wound. A protruding mass of hardened tissue, often formed after an injury but sometimes a regular feature of the plant, e.g. on the labellum of some orchids and the axis of the spikelet of some grasses. The thickened basal extension of the lemma in many grasses.

calmative adj., n. An herbal medicine that contains a mild sedative or has a calming effect.

Calvin cycle The cycle of dark reactions of photosynthesis that occurs in the chloroplasts and involves the fixation of carbon dioxide and the formation of a six-carbon sugar.

calycanthemous (L. calyx: cup; Gr. anthos: flower) adj. With a petaloid calyx.

calycate (L. calyx: cup) adj. With a calyx.

calyces See calyx.

calycifloral adj. See calyciflorous.

calyciflorate See calyciflorous.

calyciflorous (L. calyx: cup; flos, floris: flower) adj. Having the petals and stamens adnate to the calyx; applied to a subclass of dicotyledonous plants in the system of the Swiss botanist Candolle.

calyciform (L. calyx: cup; forma: shape) adj. Calyx-like in form.

calycinal adj. See calycine.

calycine (L. calyx: cup) adj. Of or pertaining to the calyx; calyx-like. Syn. calycinal.

calycinorous adj. With the petals and stamens adnate to the calyx.

calycle (L. diminutive of calyx: cup) n. A row of bracts around the calyx, resembling an outer calyx. Syn. calicle, calyculus, calycle.

calycled See calyculate,

calycoid (L. calyx: cup; Gr. eid˘: to seem, to look like) adj. Calyx-like.

calyculate (L. diminutive of calyx: cup) adj. Having bracts around the calyx or involucre imitating an outer calyx. See calycle.

calyculated See calyculate.

calycule See calycle.

calyculus See calycle.

calyptra (Gr. kalyptra: cover) n. A layer of cells that covers the developing sporophyte of mosses, liverworts, clubmosses, horsetails, and ferns. In mosses it forms a hood over the capsule and in liverworts it forms a sheath at the base of the capsule stalk. In mosses, a cap-like structure covering or partly covering the capsule and derived from the neck of the archegonium; a membranous covering of haploid tissue over the developing sporophyte, derived largely from the archegonial venter; the venter generally ruptures near the base (see epigonium), is carried upward by elongation of the seta, and frequently expands to form a protective covering over the capsule. In liverworts the structure is strictly an epigonium that generally ruptures near the apex and remains at the base of the seta, see vaginula. In a flower, a cap covering the stamens and carpels in the bud and formed by fusion or cohesion of perianth parts.

calyptrate adj. Having a calyptra.

calyx (Gr. kalyx: calyx) n. (pl. calyces, calyxes) The outer perianth whorl; a collective term for all of the sepals of a flower; the outer covering of a flower external to the corolla, which it encloses, and consisting of a whorl of leaves, or sepals, usually of a green color and less delicate in texture than the corolla; the calyx encloses the petals, stamens, and carpels and protects the flower in bud. See also pappus.

calyx bract A bract which takes the form of a petal or sepal.

calyx limb See calyx lobe.

calyx lobe The portion of the sepal which is apical, or remains free, in a fused calyx. One of the free portions of a calyx of united sepals.

calyx tooth See calyx lobe.

calyx tube Tube formed by wholly or partially fused sepals and partly by the receptacle; but not the floral tube of an epigynous or perigynous flower. Cf. hypanthium.

calyxes See calyx.

cambia See cambium.

cambium (L. cambiare: to exchange) n. (pl. cambia) A tissue composed of cells capable of active cell division, producing xylem to the inside of the plant and phloem to the outside, hence from which new wood and bark develops; it increases girth of the plant, i.e. it causes secondary growth; it is then a lateral meristem. The two most important cambia are the vascular (or fascicular) cambium and the cork cambium. The vascular cambium occurs in the stem and root; it divides to produce secondary xylem and secondary phloem (new food-conducting and water-conducting tissues). In mature stems the vascular cambium is extended laterally to form a complete ring: the sections of this ring between the vascular bundles comprises the interfascicular cambium. Cf. apical meristem.

Cambrian n. The first of six periods of the Palaeozoic Era, which began about 570 million years ago and ended about 510 million years ago. Sediments deposited during the period include the first organisms with mineralized skeletons. Common fossils include brachiopods, trilobites, ostracods, and, late in the period, graptolites. Trilobites are important in the stratigraphic subdivision of the period. The period is marked by a considerable increase in the diversit y of macroscopic marine life.

campaniform (L. campana: bell; forma: shape) See campanulate.

campanulate (L. campanella: (small) bell) adj. Bell-shaped, usually applied to a calyx and a corolla; resembling flowers of the genus Campanula; referring to a calyptra that is elongated and cylindrical.

campestral (L. campestris: of plains) adj. Growing in fields.

campestrian (L. campestris: of plains) adj. Of plains or open country.

camptodromous adj. Qualifies a pattern of venation where the secondary veins curve toward the margin without forming loops.

campylidia n. Structures to 1 mm tall shaped rather like a cat's ear, on the upper surface of foliicolous lichens, possibly acting as a splash-cup mechanism for dispersal of vegetative fragments produced on the inner surface.

campylodromous adj. of leaf venation, more or less parallel venation in which the veins originate at the base and run in incurved arches before converging at the leaf apex.

campylotropous (Gr. kampylos: curved; tropos: way) adj. Of an ovule, orientated transversely, i.e. with its axis at right angles to its stalk, and with a curved embryo sac, i.e. of an ovule curved so that the true apex or micropyle is alost at the base.

canal cells The central row of cells in the neck of an archegonium; the ventral canal cell is the most proximal, i.e adjacent to the ovum.

canaliculate (L. canaliculus: small channel, groove) adj. With a longitudinal groove or channel.

cancellate (L. cancellatus: is the shape of a lattice) adj. Latticed, or resembling a latticed construction, with a few regular, reticulate pattern; usually said of a surface such as that of an achene or seed. Cf. clathrate.

cancellina n. (pl. cancellinae) Large, empty, and usually hyaline basal leaf cells (hyalocysts); particularly those found in leaves of pottioid families such as Calymperaceae and Encalyptaceae where the hyalocysts form a well-marked lattice-like region.

cancellinae See cancellina.

candle n. The tender spring growth of the pine and some other needle-leaf evergreen species.

cane n. A slender, hollow, and often jointed stem, as in a reed; any straight, woody stem arising directly from the ground, as in the raspberry.

canescence (L. canescere: to whiten, to turn white) n. A covering of short, fine gray or white hairs producing a gray or white color.

canescent (L. canescere: to whiten, to turn white) adj. Of a plant having a whitish or grayish pubescence.

canker n. A patch of dead cells on a trunk or branches of a woody plant.

canopy (L. conopeum: mosquito net) n. The branches and foliage of a tree. Cf. bole.

canopy layer The highest stratum of growth in a forest, where the trees form almost aolid treetop canopies.

canopy trees Forest trees which have reached a size where the crown becomes part of the uppermost layer.

cano-tomentose adj. Of a density of hairs midway between canescent and tomentose.

cantharophilous adj. Entomophilous flowers that are pollinated by beetles. Cf. mellitophilous, sapromyophilous, sphigophilous.

cantharophily n. The pollination of flowers by beetles.

capability n. A measurement of the suitability of land for some particular use without permanent damage to the land. Also land capability.

capillary (Lat. capillaris: about hair) adj. Resembling hair in the manner of growth; very slender, threadlike.

capillary water The part of soil water which is held cohesively as a continuous layer around particles and in spaces, most of it being available to plant roots.

capilliform (Lat. capillus: hair; forma: shape) adj. Hair-shaped; finer than filiform.

capillitia See capillitia.

capillitium n. (pl. capillitia) Sterile filamentous elements among the spores in some gasteromycetes and Myxostelida,

Capitanian n. A stage of the Zechstein Epoch, preceded by the Wordian and followed by the Longtanian.

capitate (L. caput, capitis: head) adj. Head-like, or in a head-shaped cluster, as the flowers in many plant groups, but especially those in the dense capitate inflorescences of the Compositae (Asteraceae). Enlarged or swollen at tip, gathered into a mass at apex, as compound stigma; a knoblike stigma terminating a style. Of an inflorescence, with the flowers unstalked and aggregated into a dense cluster; of a stigma, globose, like the head of a pin. Terminated by an enlarged and rounded head.

capitellate (L. capitullum: (small( head) adj. Shaped like, or aggregated into, a very small head.

capitula See capitulum.

capitulescence n. A special term used in Asteraceae to describe a group of associated heads, it is analogus to an inflorescence.

capitulum (L. capitulum: (small) head) n. (pl. capitula) A type of flowering shoot (see racemose inflorescence) characteristic of plants of the family Compositae (Asteraceae), e.g. daisy and dandelion; the tip of the shoot is flattened and bears many small stalkless flowers (florets) surrounded by an involucre (ring) of bracts; this arrangement gives the appearance of a single flower. Also calathide, flower head.

capreolate adj. With tendrils, having tendrils.

coprophage adj. That feeds upon various fractions of faeces.

capsid bugs Green or brown bugs that suck sap of young growth, causing distortion of flowers and leaves.

capsular adj. Of or pertaining to a capsule; capsule-like.

capsule (L. capsula: small chest) n. A dry fruit that releases its seeds when ripe; it is formed from several fused carpels and contains many seeds. The seeds may be dispersed through pores (as in the poppy), through a lid (as in plantain), or by the splitting and separation of the individual carpels (as in the crocus). Various other forms of capsules include the silicula and siliqua. The part of the sporophyte of mosses and liverworts in which the haploid spores are produced. It is borne on a long stalk (seta) and sheds its spores when mature (see peristome). In most mosses it is differentiated into an apical operculum, central urn (spore-bearing region) and a sterile basal neck or hypophysis; in most liverworts and hornworts it is a uniform structure containing spores and elaters or pseudoelaters.

caput n. Of a pollen grain, an architectural element on top of a columella, discontinuous and not confluent (see tectum), Cf. baculum, intectate.

carbohydrate See carbohydrates.

carbohydrates n. A class of biochemical compounds which includes sugars, starch, chitin, and steroids.

carbonate zone A soil layer with concentrated carbonates, chiefly calcium carbonate, found most often in arid areas.

carbon cycle The process of changing atmospheric carbon into sugar by photosynthesis in plants, synthesis of more complex organic compounds in higher plants and animals, and the return to carbon dioxide by respiration or death and decay of plant and animal tissues.

carbonicolous adj. Living on coal, dependant on coal.

Carboniferous n. Penultimate period of the Palaeozoic Era, preceded by the Devonian and followed by the Permian. It began about 362.5 million years ago and ended about 290 million years ago. In Europe the lower part of the system is termed the Dinantian. It is divided into two series and is characterized by marine limestones with a rich coral-brachiopod fauna. In contrast the upper part, the Silesian, which is subdivided into three series, is noted for the deposition of terrestrial and freshwater sediments. The vast forests of the Upper Carboniferous gave rise to the rich coal measures of south Wales, England, Scotland, and many other areas worldwide. N. American geologists subdivide the Carboniferous System into two sub-systems. Of these the lower (362.5 to 322.8 million years ago) is named the Mississippian and is the equivalent of the Dinantian sub-System plus the lower part of the Silesian sub-System. The upper sub-system, the Pennsylvanian (322.8 to 290 million years ago), is the equivalent of most of the Silesian.

carboxylated iridoids A kind of route II iridoid (= normal route II) derived from epi-iridodial and epi-iridotrial via glucosylation and oxidation of C11 to the carboxyl level. Cf. decarboxylated iridoids.

carboxylic acid See fatty acid.

carbuncle n. A painful localized bacterial infection of the skin and subcutaneous tissue that usually has several openings through which pus is discharged.

carcerulus n. A dry fruit that is a type of schizocarp; it consists of a number of one-seeded fragments (mericarps) that adhere to a central axis; it has an ovary that is 4-celled at flowering and matures into 4 little pieces which split lengthwise; it is characteristic of mallow.

cardenolide See cardenolides.

cardenolides n. A subclass of triterpenoids (nortriterpenoids), basically C30 compounds made up of 6 isoprene units, composed of 23 carbon atoms, including cardiac glycosides (heart poisons and toxins) that are taken up by monarch and danaid butterflies, and also some aphids.

cardiac glycoside A kind of cardenolide.

cardioactive adj., n. Herbal medicines that can affect the heart.

carina (L. carina: hull, keel) n. A keellike part or ridge.

carinal (L. carina: hull, keel) adj. On or having relation to a ridge or keel. See carinate.

carinal canal A canal in the xylem of some sphenophytes, for example Equisetum, that results from extension and rupture of the protoxylem elements.

carinate (L. carina: hull, keel) adj. Shaped like the keel of a ship; having a longitudinal prominence on the back, like a keel, applied to a calyx, corolla or leaf; the midrib forming a keel.

cariopsis See caryopsis.

carminative adj., n. Inducing the expulsion of gas from the stomach and intestines. A drug or agent that induces the expulsion of gas from the stomach or intestines.

carnauba wax A hard high-quality wax gathered from the leaves of the Brazilian carnauba palm (Copernica cerifera) and used for making high-gloss polishes. The tree secretes the wax to prevent excess evaporation from its leaves.

carneous (L. caro, carnis: flesh) adj. Flesh-color.

carnivore (L. carnivorus: that eats flesh) n. An insectivorous plant.

carnivorous (L. caro, carnis: flesh; voro, vorare: to devour adj. that eats flesh.

carnivorous plant A plant that depends upon animal tissue for its sustenance. Carnivorous plants include some 450 species spread over several plant families and genera. Their distribution is world-wide and their habitats range from acid bog lands to semi-deserts. They attract and ensnare a range of insects and other invertebrates by means of traps. These may be of the pitfall (or passive) kind, or active and able to move as an aid to the capture of prey. The prey items provide the plant with nutrients, such as nitrogen, which are deficient in their habitats. The most active trappers include the Venus's fly-trap and the sundews, while the passive kinds are typified by the pitcher plant of North and South America.

carnose (L. caro, carnis: flesh) adj. With a fleshy texture, soft and thick.

carotene (L. carota: carrot) n. A member of a class of carotenoid pigments. Examples are beta-carotene and lycopene, which colour carrot roots and ripe tomato fruits respectively. Alpha-carotene and beta-carotene yield vitamin A when they are broken down during animal digestion; beta-carotene has antioxidant properties. Carotenes yellow, orange, or red fat-soluble (i.e. lipid-soluble) pigments which are responsible for the pigmentation of plant organs such as ripe tomatoes and peppers.

carotenoid Any of the carotenoids group. See carotenoids.

carotenoid pigment A carotene or xanthophyll pigment.

carotenoids n. A group of yellow, orange, or red pigments manufactured by bacteria, fungi, and plants and essential in the diet of animals. There are two groups-carotenes (including beta-carotene, a precursor of vitamin A) and xanthophylls. Carotenoid pigments are important for display and camouflage colouring in both plants and animals and also as eye pigments. See carotene.

carpel (Gr. karpos: fruit) n. An organ (generally believed to be a modified foliar unit) at the centre of a flower, bearing one or more ovules and having its margins fused together or with other carpels to enclose the ovule(s) in an ovary, and consisting also of a stigma and usually a style. Collectively the stigma, style and ovary; the female reproductive parts of a flower. The carpel number of a compound pistil is determined by counting the number of stigmas, styles, locules, and placentae. the carpel number is indicated by whichever of these parts is found in the greatest number. Each flower may have one carpel (monocarpellary) or many (polycarpellary), either free (apocarpous) or fused together (syncarpous). See also pistil.

carpellate adj. Of or pertaining to carpels; with carpels,

carpellode n. A non-functional carpel. Cf. pistillode.

carpid n. Half of a schizocarp, e.g., one of the winged seeds of a maple.

carpocephala See carpocephalum.

carpocephalum n. (pl. carpocephala) The sporogonial receptacle in most complex thalloid hepatics, e.g., Marchantiales.

carpogonia See carpogonium.

carpogonium (Gr. karpos: fruit; gonos: generation) n. (pl. carpogonia) The one-celled female sex organ of the red algae which, when fertilized, gives rise to the carpospores.

carpophore (Gr. karpos: fruit; phora: carrying) n. A slender prolongation of the receptacle forming a central axis between the carpels, as in the fruits of some members of the Umbelliferae (Apiaceae) and the Geraniaceae. Generally the organ that supports the carpels; specifically, a very much elongated axis to which the carpels are attached. In ferns, the stalk of a sporocarp; in a fruit, the stalk of a mericarp.

carpopodia See carpopodium.

carpopodium (Gr. karpos: fruit; pous, podos: foot) n. (pl. carpopodia) A stipe supporting an ovary; the elongation of the base of a gynoecium. Syn. gynophore, podogyne.

carpospore (Gr. karpos: fruit; spora: seed) n. A non motile spore of the red algae.

carposporophyte (Gr. karpos: fruit; spora: seed; phyton: plant) n. The post-sexual fruiting stage of a red seaweed.

carr n. A fen.

carrying capacity The maximum number of individuals of a particular species that a given area can maintain indefinitely.

cartilaginous (L. cartilago: cartilage) adj. Tough and firm but elastic and flexible, like cartilage, often somewhat hyaline.

caruncle (L. caruncula: small bit of flesh) n. A small outgrowth from the testa of a seed that develops from the placenta, funicle, or micropyle. Examples include the warty outgrowth from the castor-oil seed and the tuft of hairs on the testa of the seed of willowherb. See also aril. Syn. strophiole.

caryophyllaceous adj. Refers to members of Caryophyllaceae. Refers to petals which have a long claw at the base.

caryopsis (Gr. karyon: a nut; opsis: appearance) n. A dry single-seeded indehiscent fruit that differs from an achene in that the fruit wall is fused to the testa of the seed; the seed adheres to the thin pericarp, so that the fruit and seed are incorporated into one body. It is the grain of cereals and grasses.

cassideous adj. Shaped like a helmet or hood.

castaneous (L. castanea: chestnut) adj. Relating to or having the color of a chestnut; dark reddish-brown in color.

castanospermine A. polyhydroxy alkaloid.

casual adj, n. (Of) a weed in a cultivated field which appears occasionally but does not naturalize.

casual species Species which occur rarely in a community, such as a lilac, Syringa, but does not naturalize young plants in the area.

casuarinine n. A polyhydroxy alkaloid.

catabolism n. Destructive metabolism releasing energy and breaking down complex materials in a living organism, converting substances into excreted compounds.

catadromous (Gr. kata: down, against; dromos: race) adj. When the first branch of a frond or vein in a pinnate leaf appears on the a side facing towards the base. Living in freshwater and going to the sea to spawn.

catalpol n. A route II iridoid.

cataphyll (Gr. kata: down, against; phyllon: leaf) n. A leaf, or leaf-like organ, usually found below ground; any rudimentary leaf, as a bud scale, preceding the true foliage leaves; a scale leaf associated with a vegetative part of a plant, e.g. rhizome, perennating bud.

cataphyllary leaves Rudimentary or scale-like leaves which act as a covering of buds.

cataphylloid (Gr. kata: down, against; phyllon: leaf; eid˘: to look like) adj. Cataphyll-like.

catapult fruits Those fruits that discharge their seeds forcefully; ballistic fruits.

catarobic adj. Refers to a wet or aquatic habitat where the slow breakdown of organic matter is occurring. Organic materials are given off into the medium with much of the oxygen used, but not enough to prohibit the occurrence of aerobic organisms.

catarrh n. Inflammation of a mucous membrane, especially of the respiratory tract, accompanied by excessive secretions.

catenulate (L. catenula: small chain) adj. Chain-like, e.g. the arrangement of leaves on the stem of Aloinella and some species of Leskeaceae.

catarrhal adj. See catarrh

catarrhally adv. See catarrh

catarrhous adj. See catarrh

cathartic adj., n. Cleansing the bowels; promoting evacuations by stool; purgative; of or pertaining to the purgative principle of senna, as cathartic acid. A medicine that promotes alvine discharges; a purge; a purgative of moderate activity; the cathartics are more energetic and certain in action that the laxatives, which simply increase the tendency to alvine evacuation, and less powerful and irritaint that the drastic purges, which cause profuse, repeated, and watery evacuations

cathartical adj. See cathartic.

catkin n. An inflorescence consisting of a dense spike or raceme of apetalous, unisexual flowers as in Salicaceae and Betulaceae; an ament. Usually male catkins hang down from the stem; female catkins are shorter and often erect. Most plants with catkins are adapted for wind pollination, the male flowers producing large quantities of pollen; willows are an exception, having nectar-secreting flowers and being pollinated by insects. Syn. ament.

caudate (L. cauda: tail) adj. Having a narrow tail-like appendage; extremely acuminate; in the form of a spur.

caudex (L. caudex: stump) n. (pl. caudices, caudexes) The persistent base and often woody base of an herbaceous perennial plant; the axis or stem of a woody plant, especially of a palm or tree fern.

caudices See caudex.

caudicle n. A thread to which a pollen mass, pollinium, is attached to the stigma in the Orchidaceae and Asclepiadaceae.

caulescent (L. caulis: stem, stalk) adj. Having a well-developed, manifest stem above ground level. Cf. acaulescent.

caulicolous (L. caulis: stem, stalk; colo, colere: to inhabit) adj. Growing on the stem of plants, as certain fungi.

caulidia See caulidium.

caulidium (L. caulis: stem, stalk) n. (pl. caulidia) The main stem of mosses and leafy liverworts.

cauliferous (L. caulis: stem, stalk; ferre: to carry) adj. With a stem or stalk.

cauliflorous (L. caulis: stem, stalk; florus: flowered) adj. Bearing flowers directly on the stem or trunk as certain trees.

cauliflory (L. caulis: stem, stalk; flos, floris: flower) n. The production of flowers on the stem or trunk.

cauliform (L. caulis: stem, stalk; forma: shape) adj. Stem-like.

cauline (L. caulis: stalk, stem) adj. Of or pertaining to a stem, especially pertaining to or arising from the upper part of a stem, or as leaves arising from the stem above ground level; of leaves, borne on an aerial stem; of flowers or fruits, borne on old wood.

caulis (L. caulis: stem, stalk) n. The main stem of a herbaceous plant.

caulocarpic (L. caulis: stem, stalk; karpos: fruit) adj. Of plants having the stem living for many years, bearing flowers and fruits.

caulocarpous (L. caulis: stem, stalk; karpos: fruit) adj. Bearing fruit year after year on the same stems.

caulogenic initial A stem or branch initial.

cauloid (L. caulis: stem, stalk; Gr. eid˘: to be like) adj. Stem-like.

caulome n. A collective term for all stems of a plant and their modifications.

caulonema n. (pl. caulonemata) The secondary, bud-generating part of the filamentous moss protonema, typically reddish-brown, having few chloroplasts and consisting of long cells with oblique end walls. Cf. chloronema, protonema.

caulonemata See caulonema.

cecidia See cecidium.

cecidium n. (pl cecidia) An abnormal growth caused by insects or fungal infection. Syn. gall. Galls can take a wide variety of forms, but most frequently occur as swellings or pits in stems, roots, leaves, and buds. Organisms responsible for their formation include bacteria, viruses, fungi, nematodes, mites, and insects. The gall structure can be quite complex, with several distinct cell layers, or relatively simple and undifferentiated, but is typically very distinct from surrounding normal tissue and often is characteristic of the eliciting organism. It can involve cell enlargement (hypertrophy) or cell proliferation (hyperplasia). The mechanisms underlying gall formation are known in only a few cases. The bacterium Agrobacterium tumefaciens, which is responsible for crown galls, induces a genetic change in infected host tissue by transfer of a plasmid bearing tumour-forming genes. Insects may secrete substances in their saliva that induce gall formation, or in some cases may transmit viruses or other genetic 'carriers' that affect the plant genome.

cell (L. cella: little room) n. As used in plant identification, a hollow cavity or compartment within a structure, as the cavity of the anther containing pollen or the cavity of the ovary containing ovules; a locule.

cell lineage See lineage pattern.

cell membrane A semipermeable limiting layer of cell protoplasm. Syn. plasma membrane, plasmalemma.

cellular (L. cellula: cell [of a monk]) adj. Made up of small cavities or compartments. Syn. cellulate.

cellulate See cellular.

cellulose (L. cellula: cell [of a monk]) n. The chief substance composing the cell walls or woody part of plants; a carbohydrate polymer of the simple sugar glucose, of unknown molecular structure, but having the composition represented by the empirical formula (C6H10O5)x. It is found in the cell walls of plants and green algae, as well as dinoflagellates. Cellulose is the most abundant compound on earth that is manufactured by living things.

cell wall Any tough layer which surrounds a cell and its cell membrane. In plants, this wall is composed of cellulose.

cenanthy (Gr. kenos: empty; anthos: flower) n. The absence of stamens and pistils in a flower, i.e. the perianth is empty.

cenospecies n. All the ecospecies that may exchange genes through hybridization, like the violets, Viola.

Cenozic See also Cenozoic.

Cenozoic (Gr. kainos: new; z˘on: animal) n. Era of geologic time extending from about 65 million years ago to the present. It includes the Tertiary and Quaternary Periods: the so-called ages of mammals and man. molluscs and microfossils are used in the stratigraphic subdivision of the era. The Alpine-Himalayan orogeny reached its climax during this period of geologic time. Also Cenozic.

center of dispersal The geographic area from which a taxon has spread or is spreading, such as where an alien plant was introduced.

center of diversity A specific locality with high levels of genetic or species variance.

center of endemism A unique geographic region with species which are known only to that area. Cf. endemic.

center of origin The geographic area in which a taxon originated and from which it is spread.

central cell The large cell initially usually containing two nuclei (polar nuclei) that makes up the bulk of the eight-nucleate embryo sac, see also antipodals, egg cell, synergids. See guide cells.

central strand The middle of many moss stems is made up of a bundle of much narrower and more slender cells, usually colored and thin-walled in transverse section, known as the 'central strand'. This is usually continuous with the midrib or costa of the leaves, similar to the vascular bundles in the higher plants. Also axial strand.

centrifugal (L. centrum, centri: center; fuga: flight, escape) adj. Directed, or developing, from the centre or axis outwards.

centrifugal inflorescence A flower cluster developing from the center outwardas in a cyme.

centripetal (L. centrum, centri: center; petere: to seek) adj. Directed, or developing, from the outside towards the centre or axis, as in the head of a sunflower, in which the oldest flowers are near the edge and the youngest flowers are in the center.

centripetal inflorescence A flower cluster developing from the edge toward the center, as in a corymb

centripetally adv. See centripetal.

centromere (L. centrum: center; Gr. meros: part) n. The region of a chromosome by which it attaches to the spindle during meiosis and mitosis. Also kinetochore.

centrosome (L. centrum: center; Gr. s˘ma: body) n. A minute, protoplasmic body, regarded as the active center of cell division, in mitosis.

centrum (L. centrum: center) n. Central portion. (In lichens) the perithecial chamber enclosed by the exciple.

cephalanthia See cephalanthium.

cephalanthium n. (pl. cephalanthia) The flower head of a Compositae species.

cephalia See cephalium.

cephalium n. (pl. cephalia) A woolly growth at the top of the stem of some cacti, such as Melocactus, on which the flowers appear.

cephalodia See cephalodium.

cephalodium (Gr. kephalŕ: head) n. (pl. cephalodia) A gall-like outgrowth on the thallus of certain lichens, containing an alga different from that of the lichen. Generally cephalodia contain cyanobacteria (e.g., Nostoc) while the rest of the thallus has a green photobiont (e.g., Trebouxia). Nostoc heterocysts in cephalodia fix. atmospheric nitrogen. Genera containing cephalodia include: Coccotrema, Lobaria, Placopsis, Psoroma, Psoromidium, Pseudocyphellaria, Solorina, Stereocaulon and Sticta.

ceraceous (L. cera: wax) adj. Waxy in texture or appearance.

ceratolin n. A dihydrochalcone.

cerebriform adj. Convoluted, brain-like.

ceriferous (L. cera: wax; ferre: to carry) adj. Producing or secreting wax, as a gland. See cerogenous.

cernuous (L. cernuus: falling forwards, face down) adj. Drooping, nodding or bowing down, as a flower; nodding.

cerogenous (Gr. kŕros: wax; genna˘: to produce) adj. Wax producing.

certified seed A class of certified seed that is the progeny of Breeder, Foundation, or Registered seed... and is produced and handled under procedures established by the certifying agency for the purpose of maintaining genetic purity and identity. Seed used for commercial crop production produced from foundation, registered, or certified seed under the regulation of a legally constituted agency.

cerulean (L. cŠrulus: blue, dark blue) adj. Deep blue, sly blue, azure.

cerulescent See caerulescent.

cespitose See caespitose.

cestode n. A parasite intestinal worm having a flattened, bandlike form.

C horizon In soils, the partly weathered rock fragments which are the parent materials for the upper A horizon and B horizon. This is occasionally lacking. Cf. D horizon.

chafers n. Beetles that attack plant roots as larvae and leaves as adults.

chaff n. Thin, dry, membranous scales or bracts, as those on the receptacle subtending the flowers in the heads of certain Compositae (Asteraceae). Thin, dry unfertilised ovules among the fully developed seeds of a fruit. The seed coverings and other debris separated from the seed in threshing grain.

chaffy adj. With chaff; chaff-like.

chalaza (Gr. khalaza: hard grain in an egg yolk) n. The part of an ovule or seed where the integuments are connected to the nucellus, at the opposite end from the micropyle, i.e. the part of an ovules to which the end of the stalk (funicle) is attached.

chalazal adj. Of or pertaining to the chalaza.

chalazogamy n. Fertilisation during which the pollen tube penetrates the ovule by way of the chalaza. Cf. mesogamy, porogamy.

chalazosperm n. The nutritive tissue in a seed, developed from persistent chalazal cells. Cf. endosperm, primary endosperm, perisperm.

chalcone See chalcones.

chalcones n. Flavonoids isomeric with flavanones, the A ring being derived from acetate and with a phloroglucinol oxidation pattern, the B ring from a phenylpropanoid precursor, and with an allyl bridge (-CH:CH.CO) separating the two rings, often yellow, but turning orange-red in the presence of ammonia.

chalk n. Soft gray, buff, or white limestone formed from the shells of foraminifers.

chamaephyte (Gr. khamai: on the ground; phuton: plant) n. Woody or herbaceous evergreen perennial from 10 to 20 inches tall or whose shoots die back periodically. These plants are small shrubs covered by snow in the winter. A plant which produces resting buds that are near or just above the ground; e.g. Vaccinium angustifolium.

chambered adj. With hollow spaces. Of pith, divided into empty horizontal chambers by cross partitions.

Changxingian n. 1. The final age in the Late Permian period (Zechstein Epoch), preceded by the Longtanian, followed by the Griesbachian Age (Triassic), and dated at 254 to 248 million years ago. 2. The corresponding eastern European stage which, because of correlation problems, has been included in the Triassic system. It is roughly contemporaneous with the Bundsandstein (western Europe), upper Amarassian (New Zealand), and upper Ochoan (N. America). Syn. Tatarian, Tartarian.

channeled adj. Having one or more longitudinal grooves; hollowed out like a gutter and semicircular in cross-section. Cf. keeled.

chaparral n. A vegetation type consisting of dense thickets of evergreen shrubs.

character (Gr. kharaktŕr: sign, mark) n. Heritable trait possessed by an organism; characters are usually described in terms of their states, for example: 'hair present' vs. 'hair absent,' where 'hair' is the character, and 'present' and 'absent' are its states. Expression of a gene or group of genes. An attribute of an organism resulting from the interaction of a gene or genes with environment. Also characteristic.

character reversal Character that reverses to a more ancestral state.

character state The state or value of a character; for example some character states for the character 'color' are red, green and blue

characteristic See character.

characteristic diversity The pattern of distribution and abundance of habitats and their species populations under conditions where human influence on the ecosystem is no greater than that of any other biotic factor.

Charophyceae n. A class (in some classifications a division: Charophyta) of algae that in some ways resemble bryophytes (Bryophyta). They occur in fresh and brackish water and their calcified fructifications are ornamented with spiral striae. Neglected by geologists until 1959, they are now used as stratigraphic markers in Cenozoic strata.

charophyta See Charophyceae.

Charophyta See Charophyceae.

charophyte n. A member of the Charophyceae.

Charophytes n. Members of the Charophyceae.

chartaceous (L. chartaceous: made of paper) adj. Having the texture of thin but stiff paper, usually not green; papery; e.g. the leaves of Ptychomnion, the bud scales of Vaccinium angustifolium.

chart quadrat A cart or map of a sample area showing the placement and area of each plant.

chasmocolous adj. Dwelling in crevices or cracks.

chasmogamous (Gr. chasma: opening; gamos: marriage) adj. Applied to flowers which open before fertilization and are usually cross-pollinated. Cf. cleistogamous.

chasmogamy (Gr. chasma: opening; gamos: marriage) n. The opening of the perianth of a flower for the purpose of fertilization.

chasmophyte (Gr. chasma: opening; phyton: plant) n. A plant tha grows in the crevices of rocks. Cf. chomophyte.

chelate v. See chelation.

chelation n. The process whereby an organic chemical bonds with and removes free metal ions from solutions.

chelator n. See chelation.

chelidonic acid An organic acid derived from a condensation of C3 and C4 units related to phosphoenolpyruvic acid and erythrose-4-phosphate.

chemical stratification A condition found in temperate lakes during the summer and winter stagnation periods in which certain horizontal layers become different chemically from adjacent ones, often causing turnover. Cf. thermal stratification.

chemiosmotic theory A theory postulated by the British biochemist Peter Mitchell (1920-92) to explain the formation of ATP in the mitochondrial electron transport chain. As electrons are transferred along the electron carrier system in the inner mitochondrial membrane, hydrogen ions (protons) are actively transported (by proton pumps) into the space between the inner and outer mitochondrial membranes, which thus contains a higher concentration of protons than the matrix. This creates an electrochemical gradient across the inner membrane, down which protons move back into the matrix. This movement occurs through special channels associated with ATP synthetase, the enzyme that catalyses the conversion of ADP to ATP, and is coupled with the phosphorylation of ADP. A similar gradient is created across the thylakoid membranes of chloroplasts during the light reaction of photosynthesis (see photophosphorylation).

chemoautotrophe n. See chemoautotrophic.

chemoautotrophic adj. Being autotrophic and oxidizing an inorganic compound as a source of energy, as a chemoautotrophic bacteria.

chemolithotrophe n. See chemolithotrophic.

chemolithotrophic adj. Describes an organism which obtains its energy from the oxidation of inorganic compounds.

chemonastic adj. Regarding the chemically-induced movement of plant parts.

chemoorganotrophe n. An organism, especially a microorganism, that obtains its energy by the oxidation of organic compounds.

chemoorganotrophic adj. Describes a heterotroph which oxidizes chemical bonds for energy but requires organic carbon compounds to grow. Cf. chemoorganotroph.

chemosynthesis n. A type of autotrophic nutrition in which organisms (called chemoautotrophs) synthesize organic materials using energy derived from the oxidation of inorganic chemicals, rather than from sunlight. Most chemoautotrophs are bacteria, including Nitrosomonas, which oxidizes ammonium to nitrite; and Thiobacillus, which oxidizes sulphur to sulphate.

chemotaxis n. The movement of an organism caused by a chemical stimulus.

chemotrophe n. See chemotrophic.

chemotrophic adj. Refers to an organism that produces energy from a chemical reaction which does not depend on light. Cf. heterotrophic, autotrophic, phototrophic.

chemotropism n. Movement or growth of cells or organisms in response to chemical stimuli.

chemotype n. A population of plants belonging to a particular species that differs chemically from others of that species.

cheradophilous adj. Thriving on wet sand; growing on sand bars.

chernozem n. A zonal group of soils with deep fertile surface soil, dark brown to black in color, rich in organic matter, grading into lighter colored soil below, and having a calcium carbonate layer at a depth of 1.5 to 4 feet (45 to 120 cm.). These are often found under tall grasslands in a temperate to cool, somewhat humid climate. Syn. black earth.

chersophilous adj. Thriving in dry places.

chert n. A type of rock; chert can form as a primary deposit preserving fossils within it, or replace organic materials in fossils embedded in different rock material.

Chesterian n. A series in the Mississippian of N. America, underlain by the Meramecian and overlain by the Morrowan. It is roughly contemporaneous with the Brigantian Stage of the Visean Series and the Serpukhovian Series. The Springerian is an alternative name for the upper part of the Chesterian.

chestnuts soils A zonal group of soils with dark brown surface horizons grading into lighter colored soil below, and a calcium carbonate layer at depths of one to four feet (30 to 120 cm.). These are associated with grasslands in temperate to cool, subhumid to semiarid climates; moister than brown soils, drier than chernozem.

chianophile adj. A plant that can endure long snowy winters, or one that requires snow cover in winter.

chianophobe adj. A plant that does not tolerate long snowy winters, or one that can survive with little or no snow cover during winter.

chiasma n. An exchange of partners between paired chromatids in the first division of meiosis.

chimaera See chimara.

chimara n. A plant formed of the tissues of two different species mingled together and being intermediate in characteristics between the two parents; a mixture of tissues of genetically different constitution in the same part of a plant; it may result from mutation, irregular mitosis, somatic crossing-over, or artificial fusion of unlike tissues (e.g., a `graft hybrid'). Also chimera, chimaera.

chimera See chimara.

chiral adj. Of or relating to the structural characteristic of a molecule that makes it impossible to superimpose it on its mirror image.

chirality n. The right or left handedness of an asymmetric molecule. An object or a system is called chiral if it differs from its mirror image. A chiral object and its mirror image are called enantiomorphs or, when referring to molecules, enantiomers. A non-chiral object is called achiral or, at times, amphichiral.

chiropterophilous adj. Of a kind of zo÷philous pollination, flowers pollinated by bats, with a distinctive morphological syndrome (e.g. dull color, robust, presented so access is easy). cf. entomophilous, cantharophilous, mellitophilous, sapromyophilous, sphigophilous, ornithophilous.

chiropterophily (Gr. kheir, kheros: hand; pteron: wing; philos: friend, loved) n. Pollination of plants by bats, e.g. Agave, Bombaceae.

chitin (Gr. khit˘n: tunic) n. A Carbohydrate polymer found in the cell walls of fungi, and in the exoskeletons of arthropods.

chlamydeous (Gr. khlamis: cloak, mantle) adj. With or pertaining to, a floral whorl.

chlamydospore (Gr. khlamis: cloak, mantle: spora: seed) n. A thick-walled, asexual, resting spore of certain fungi and algae.

chledophilous adj. Thriving in waste land habitats.

chloranthous (Gr. chloros: light green, greenish yellow; anthos: flower) adj. With green, leaf-like flowers.

chloranthoid adj. Of a leaf tooth with a clear persistent swollen cap, medial secondary or tertiary vein accompanied by (1) 2 higher-order laterals that enter the apex or fuse with the medial.

chloranthy (Gr. chloros: light green, greenish yellow; anthos: flower) n. The state or condition of having green, leaf-like flowers.

chlorenchyma tissue Parenchyma cell containing chloroplasts found in plants.

chlorocyst n. Geen (chlorophyllose) cell; generally used in contradistinction to hyalocysts; e.g. leaves of Sphagnum, Leucobryum, or Calymperes.

chlorogenic acid A type of phenylpropanoid; caffeic acid linked to quinic acid.

chloronema n. (pl. chloromenata) The primary photosynthetic part of the moss protonema, typically green, having numerous chloroplasts and consisting of short cells with perpendicular end walls. Cf. caulonema, protonema.

chlorophycean adj. Having the grass-green colour and other essential characteristics of the Division Chlorophyta.

chlorophyll (Gr. chloros: light green, greenish yellow; phullon, leaf) n. Pigments constituting the green colouring matter of plants and absorbing radiant energy in photosynthesis. It includes a porphyrin ring, and often has a long hydrophobic tail.

chlorophyllose See chlorophyllous.

chlorophyllous (Gr. chloros: light green, greenish yellow; phullon: leaf) adj. Of or containing chlorophyll; generally green unless masked by some other pigments. Syn. chlorophyllose.

Chlorophyta (Gr. chloros: light green, greenish yellow; phyton: plant) n. A large phylum of algae, the members of which possess chlorophylls a and b, store food reserves as starch, and have cellulose cell walls. In these respects they resemble plants more closely than do any of the other algal phyla. The Chlorophyta are widely distributed and diverse in form. Unicellular forms may occur singly (sometimes with flagella for motility) or in colonies, while multicellular forms may be filamentous (e.g. Spirogyra) or platelike (e.g. Ulva).

chloroplast (Gr. chloros: light green, greenish yellow; plastos: modelled, formed) n. Any of the chlorophyll-containing organelles (see plastid) that are found in large numbers in those plant and algal cells undergoing photosynthesis. Plant chloroplasts are typically lens-shaped and bounded by a double membrane. They contain membranous structures called thylakoids, which are piled up into stacks (see granum), surrounded by a gel-like matrix (stroma). The light reaction of photosynthesis occurs on the thylakoid membranes while the dark reaction takes place in the stroma.

chloroplast DNA Chloroplasts are the typical organelles of green plants. They are the site of photosynthesis though they perform a number of further synthetic processes. Chloroplasts may represent an ancient symbiotic relationship between photosynthetic bacteria and eukaryotic cells. Chloroplasts also contain genetic information; they have a small amount of DNA, similar to that of bacteria, and replicate themselves through a fission process. Chloroplast DNA is a circular molecule ranging from 120 to 217 kilobase pairs in photosynthetic land plants. The chloroplast genome is about 134 kb in grasses (134,000 bases long). Chloroplast DNA is unlike the genomic DNA of a plant because it is inherited in a non-Mendelian mode. It is inherited from one parent only and because of this, does not undergo recombination and has a highly conserved gene order. Chloroplast DNA is inherited maternally in most angiosperms and evolves relatively slowly; thus, it is a reliable indicator to trace maternal ancestry. Chloroplast DNA sequences have then become a useful tool for the study of plant taxonomy, phylogeny, and population genetics. Chloroplast DNA is highly conserved. This means that it doesn't have a high rate of mutation or change. Inversions and other rearrangements are uncommon in flowering plant chloroplast DNA. Also cpDNA.

chloroplastic adj. Related to chloroplast.

chlorosis (Gr. chloros: light green, greenish yellow) n. Abnormal condition characterized by absence of green pigments in plants. A form of anemia named for the greenish tinge of the skin of a patient. Its symptoms included lack of energy, shortness of breath, dyspepsia, headaches, a capricious or scanty appetite and amenorrhoea. Today this disease is diagnosed as hypochromic anemia.

chlorotic (Gr. chloros: light green, greenish yellow) adj. Lacking chlorophyll. See chlorosis.

cholagogue adj., n. Promoting the discharge of bile from the system. An agent which promotes the discharge of bile from the system.

cholesterol (Gr. kholŕ: bile; stereos: solid, firm) n. A compound derived from steroids and found in many animal tissues. Cholesterol is manufactured by the liver and other tissues and its derivatives form constituents of cell membranes, bile, blood, and gallstones. It is present in the bloodstream in the form of lipoproteins (see lipid), of which there are several types. Cholesterol and other lipids are transported from the liver to the tissues in the form of low-density lipoproteins (LDLs); they are conveyed from the tissues to the liver to be broken down as high-density lipoproteins (HDLs). High levels of LDL-cholesterol in the blood (over 4.4 mmol/l) are associated with an increased risk of heart disease, as a result of fatty deposits in the walls of arteries. See also atherosclerosis.

chomophyte n. A plant that grows on rock fissures or crevices, on rocky ledges. Cf. chasmophyte.

chondriocont (Gr. khondrion, diminutive of khondros: grain; kontos: rod) n. A rodlike or threadlike mitochondrion.

chondriome (Gr. khondrion, diminutive of khondros: grain) n. The mitochondria of a cell, considerd as a whole.

chondriomite (Gr. khondrion, diminutive of khondros: grain; mitos: thread) n. A chain of granular mitochondria; a single granular mitochondrion.

chondriosome (Gr. khondrion, diminutive of khondros: grain) n. See mitochondrion.

chondroid adj. Tough, cartilaginous.

Chordata n. A phylum of animals characterized by a hollow dorsal nerve cord and, at some stage in their development, a flexible skeletal rod (the notochord) and gill slits opening from the pharynx. There are four subphyla: the Urochordata (sea squirts), Cephalochordata (lancelets), Agnatha (jawless chordates), and Gnathostomata (jawed chordates). In the Agnatha and Gnathostomata, commonly known as vertebrates or craniates, the notochord is present only in the embryo or larva and becomes replaced by the vertebral column (backbone) before birth or metamorphosis. This has permitted the vertebrates a greater degree of movement and subsequent improvement in the sense organs and enlargement of the brain, which is enclosed in a skeletal case, the cranium. In some classifications the two nonvertebrate subphyla are elevated to the status of phyla and the jawed and jawless chordates are included together in a third phylum, Craniata, containing a single subphylum, Vertebrata. The old subphyla Agnatha and Gnathostomata are then regarded as superclasses of the Vertebrata. The first chordates and the earliest vertebrates (Craniata) are both found in Cambrian rocks.

chordate n. Any of a phylum (Chordata) of animals having at least at some stage of development a notochord, dorsally situated central nervous system, and gill clefts and including the vertebrates, lancelets, and tunicates.

choripetalous (Gr. kh˘ris: apart; petalon: leaf) adj. Polypetalous; having unconnected or separate petals. See apopetalous or polypetalous.

chorisantherous (Gr. kh˘ris: apart; anthŕros: flowered) See apostemonous.

chorisepalous (Gr. kh˘ris: apart; sepalous: see sepal) See polysepalous.

chorological adj. Related to chorology.

chorology n. The science which treats of the laws of distribution of living organisms over the earth's surface as to latitude, altitude, locality, etc.

chresard n. The water in soil that is available to plants for absorption.

chromatid n. One of the usually paired and parallel strands of a duplicated chromosome joined by a single centromere. A longitudinal half-chromosome that appears between the early prophase and metaphase stages of somatic mitosis and between the diplotene (at least) and the second metaphase stage in meiotic mitosis. One of two threadlike structures formed by the longitudinal division of a chromosome during meiotic prophase and known as a daughter chromosome during anaphase.

chromatin n. Material of the nucleus and chromosomes which can be stained deeply with certain dyes.

chromatophore n. In plants, a plastid which contains pigment in a cell such as a chromoplast or chloroplast. In animals, a cell or group of cells with pigment having the capability of color change.

chromoalkaloid See chromoalkaloids.

chromoalkaloids n. Same as betalains.

chromone n. A type of coumarin consisting of a benzene ring fused to a pyrone ring with a methyl group at the C2 position and oxygenated at the C5 and C7 positions.

chromoplast (Gr. khr˘ma: color; plastos: formed, modelled) n. Any of various organelles in plant cells that contain pigments. Red, orange, and yellow chromoplasts contain carotenoid pigments, while green chromoplasts (called chloroplasts) contain the pigment chlorophyll and provide the green coloration of most plants. Cf. leucoplast, plastid.

chromosome (Gr. khr˘ma: color; s˘ma: body) n. A thread-like structure in the nucleus of a cell, containing a linear sequence of genes, which determine hereditarily cell structure and function. A thread-like structure in the nucleus of eukaryotic cells composed of DNA and protein. Chromosomes carry the genetic information of the cell in their DNA, organized into linear arrangements of genes. The locations of genes on particular chromosomes and their relative positions along the chromosome can be mapped by classic breeding experiments, or by more recent techniques for probing specific DNA sequences (See DNA probe). Chromosomes can be observed directly in cells only while they are dividing. Each species has a constant chromosome number; humans have 23 pairs of chromosomes. One of the threadlike structures that carry the genetic information (see gene) of living organisms and are found in the nuclei of their cells. Chromosomes consist of a central axis of DNA with associated RNA and proteins. Before cell division, the long filamentous threads contract and thicken and each chromosome can be seen as two identical threads (chromatids) joined at the centromere. During cell division the chromatids separate to become the daughter chromosomes (see mitosis). Chromosome number is characteristic of a species. For example, a normal human body cell has 46 chromosomes comprising 22 matched pairs (called autosomes) and two sex chromosomes. A human sperm or egg cell has half this number of chromosomes (see meiosis). Abnormal numbers or parts of chromosomes often lead to abnormalities in the individual concerned. Down's syndrome is caused by the presence of an extra number 21 chromosome.

chromosomic adj. See chromosome.

chron (Gr. khronos: time) n. 1. A small unit of geologic time, equivalent to the chronostratigraphic unit chronozone, usually based on fossil zonation (see Biochron). When used formally (e.g. Gilbert Chron) the initial letter is capitalized. 2. A single time interval of constant polarity of the geomagnetic field (polarity chron).

chronospecies (Gr. khronos: time; L. species: type) n. According to one view of evolution (that of phyletic gradualism), a new organism may be derived from its ancestor by a process of slow, steady evolutionary change. Conceivably, the descended organism might not be regarded as a member of the same species as its ancestor, in which case it would constitute a new species, in particular a chronospecies.

chronostratigraphic unit The sequence of rocks formed during a discrete and specified interval of geologic time. Chronostratigraphic units are ranked, according to the length of time they record, into erathems (the longest), systems, series, stages (the basic working unit), and chronozones (the shortest). Each unit comprises a number of units of lower rank, e.g. a system would consist of a number of series, and, similarly, a number of stages would constitute a series. All the rocks formed anywhere in the world, regardless of lithology or local thickness, would be referred to the chronostratigraphic unit appropriate to their time of formation, e.g. all rocks laid down in the Cambrian Period belong to the Cambrian System. In the traditional stratigraphic scales, however, note that chronostratigraphic units, and the geologic-time units to which they correspond, have been defined on the basis of a type section (see Stratotype), so historically it is the chronostratigraphic unit that has determined the geologic-time unit and not vice versa. See Chronostratigraphy; and Stratigraphic Nomenclature.

chronostratigraphy (Gr. khronos: time; L. stratum: layer; graphŕ: writing) n. Branch of stratigraphy linked to the concept of time. In chronostratigraphy, intervals of geologic time are referred to as chronomeres. These may be of unequal duration. Intervals of geologic time are given formal names and grouped within a Chronomeric Standard hierarchy. The formal terms are: eon, era, period, epoch, age, and chron. The last four of these are the equivalent of system, series, stage and chronozone in the Stratomeric Standard hierarchy. The formal terms are written with initial capital letters when accompanied by the proper names of the intervals to which they refer. Some geologists hold that the term chronostratigraphy is synonymous with biostratigraphy, but most agree that the two branches are separate.

chronozone (Gr. khronos: time; z˘nŕ: belt) n. The lowest-ranking chronostratigraphic unit. The duration of a chronozone is defined by a type section which may be based on a biostratigraphic zone (in which case it would include all rocks laid down during that time interval regardless of fossil content or rock type), or it may be defined on the basis of the time span of an existing lithostratigraphic unit. With increasing knowledge, chronozone boundaries may be found not to coincide with the boundaries of the stages to which they belong, and stages may more precisely be divided into substages. The geologic-time unit equivalent to a chronozone is a chron.

chrysalid See chrysalis.

chrysalis n. (pl. chrysalises or chrysaliĚdes) An insect in the stage between larva and adult, when it is in a cocoon. The pupa of insects that undergo metamorphosis, e.g. butterflies, moths. The protective case that surrounds the pupa. Also chrysalid.

chrysanthine (Gr. khrysos: gold; anthŕ: flowering) See chrysanthous.

chrysanthous (Gr. khrysos: gold; anthos: flower) adj. With yellow flowers.

chrysocarpous (Gr. khrysos: gold; karpos: fruit) adj. With golde, yellow fruit.

chrysophanol n. An anthraquinone.

Chrysophyta n. A taxonomic division containing diatoms, golden-brown algae, and yellow-green algae, all single-celled and normally found in marine environments.

chylocaulous adj. Refers to fleshy stems, like cactus.

chylophyllous adj. Refers to fleshy leaves, like agave.

cicatrice (L. cicatrix: scar) n. A scar, such as the scar produced when a leaf separates from the stem.

cicatrix (L. cicatrix: scar) See cicatrice.

cilia See cilium.

ciliate (L. cilium: eyelid, eyelash, eyebrow) adj., n. With marginal hairs that form a fringe; having cilia. A protozoan of the phylum Ciliophora, bearing cilia. Syn. ciliated. Cf. fimbriate.

ciliated See ciliate.

ciliation n. Group of straight and stiff hairs on leaves, petals, sepals, bracts, etc.

ciliolate (L. cilium: eyelid, eyelash, eyebrow) adj. With a marginal fringe of minute hairs.

Ciliophora (L. cilium: eyelid, eyelash, eyebrow; Gr. phora: carrying) n. A phylum of the Protoctista containing ciliated protozoa - ciliates - (including Paramecium) that possess two types of nuclei, a micronucleus and macronucleus. The cilia are used for feeding and locomotion. Ciliates reproduce sexually by conjugation. A phylum of microscopic single-celled organisms (see protozoa), the ciliates, having two nuclei and tracts of hairlike cilia over the cell surface, used for feeding and swimming. Most are free-swimming (see Paramecium) but some are attached to the substrate by a stalk (see Stentor; Vorticella). Most ciliates feed on organic detritus, other protozoans, etc., but some are parasitic, especially on fish and other aquatic animals.

cilium (L. cilium: eyelid, eyelash, eyebrow) n. (pl. cilia) A small hair or hairlike process, usually along the margin of a structure. In unicellular plants, gametes, spores etc., minute hair-like protoplasmic protrusions whose movement confers motility on the cell; in higher plants, hairs more or less confined to the margins of an organ. In mosses, a delicate, hair-like or thread-like structure mostly one cell wide and unbranched (opposed to lacinia); in peristomes the structures frequently found singly or in groups alternating with the segments of the inner peristome; also applied to hair-like appendages fringing leaves or calyptrae.

cincinnal adj. Refers to scorpoid cymes and other curled floral arrangements.

cincinnus (L. cincinnus: curl of hair) n. (pl. cincinni) A monochasial, cymose inflorescence with flowers arising alternately from one side of an axis then the other. A spirally curled cymose inflorescence. A dense helicoid cyme with the pedicels short on the developed side.

cineraceous See cinereous.

cinereous (L. cinereus: ashen) adj. Ash-colored; grayish due to a covering of short hairs. Also cineraceous.

cinnamic acid A simple phenol derived from L-phenylalanine, involved in formation of phenylpropanoids, occurring in various aromatic resins.

cinnamic adj. Of or obtained from cinnamon. Of or pertaining to cinnamic acid or its derivatives.

cinnamomeous adj. Cinnamon-colored.

circinate (L. circinatus: rounded) adj. Rolled into a coil, from the tip downward, with the apex at the centre, as in the young leaves of a fern; curved in a circle, e.g. leaves of Hypnum circinale.

circinotropous adj. Said of an ovule, with a long funicle curved so that the ovule is held upside-down. Cf. amphitropous, anatropous, atropous, campylotropous, hemitropous.

circle of vegetation All of the species and communities that are restricted to a natural vegetation unit.

circum- (L. circum: around) prefix. Meaning around, as around an object or structure.

circumboreal adj. Said of plants which surround the Northern Hemispere, appearing in both the Old and New Worlds, such as the dandelion. Cf. circumpolar.

circumneutral adj. Term applied to water with a pH of 5.5 (acidic) to 7.4 (alkaline).

circumnutate (L. circum: around; nutare: to sway, totter) adj. Of the apex of a stem or other growing part of a plant: to bend or move around in an irregular circular or elliptical path.

circumpolar adj. Refers to species that occur all around the poles in either the north or south and in both the eastern and western hemispheres. Cf. circumboreal.

circumsessile adj. Dehiscing along a transverse circular line around the fruit or anther, so that the top separates or falls off like a lid. Also circumscissile.

circumsciss (L. circumcidere: to cut around) v. To break open along a transverse line around the circumference.

circumscissile (L. circumcissus: cut around) adj. Opening and splitting by a transverse fissure around the circumference, leaving an upper and lower half; said of certain seed pods or capsules. Dehiscing along a transverse circular line, so that the top separates like a lid.

cirque n. A deeply-eroded area with steep slopes in a region of past glaciers.

cirrate (L. cirrus: curl) adj. Curled; wavy; with cirri; e.g. awn. Also cirrhous.

cirrhiferous adj. See cirriferous.

cirrhose See cirrose.

cirrhous (L. cirrus: curl) adj. Terminated by a tendril, being a projection of the midrib. Also cirrhose, cirrate.

cirriferous (L. cirrus: curl; ferre: to carry) adj. Bearing a tendril. Syn. cirrhiferous.

cirrose (L. cirrus: curl) adj. With cirri; ressembling a cirrus. Syn. cirrhose. Also cirrate.

cirrus (L. cirrus: curl) n. (pl. cirri) A tendril.

citation n. n botanical systematics, a quotation from a book or author referencing an authority or precedent.

citriform adj. Lemon-shaped. Also limoniform.

cismontane adj. Referring to the ocean-facing side as opposed to the desert-facing side of the mountains.

CITES The Convention on International Trade of Endangered Species, which provides regulations for the international trade in listed species of plants and animals. Also C.I.T.E.S.


citreous (L. citreus: form citrus tree) adj. Lemon-yellow, greenish-yellow.

cladautoicous adj. With the androecium on separate branches. Cf. autoicous.

clade (Gr. klados: branchlet, branch) n. A monophyletic taxon; a group of organisms which includes the most recent common ancestor of all of its members and all of the descendants of that most recent common ancestor. A group of organisms formed by a complete line of living beings, including the first founding species of the line and all of its descendents (e.g. mammals). It is the only taxonomic category recognized by most systematists. In contrast, paraphyletic groups, which are a truncated line of descent (e.g. fish), and polyphyletic groups, which are made up of several lines of descent (such as algae), are not currently recognized in taxonomy. Syn.: monophyletic taxon.

cladia See cladium.

cladicarpous (Gr. klados: branchlet, branch; karpos: fruit) adj. See pleurocarpous.

cladism See cladistics.

cladistic (Gr. klados: branchlet, branch) See cladistics.

cladistically adv. About cladistics. See cladistics.

cladistics (Gr. klados: branchlet, branch) n. (n. pl. usually treated as singular) A system of biological taxonomy that defines taxa uniquely by shared characteristics not found in ancestral groups and uses inferred evolutionary relationships to arrange taxa in a branching hierarchy such that all members of a given taxon have the same ancestors. (noun plural but singular in construction) A system of classification of living organisms in which species are allocated to groups (called clades) on the basis of shared characteristics that are thought to indicate common ancestry. For example, all organisms with mammary glands would form the clade mammals. The relationship of the various clades is represented on a diagram (cladogram). The cladogram can be taken as reflecting the evolutionary relationships of the clades. This assumes that new species are formed by the sudden splitting of two new forms from the ancestral form, in opposition to neo-Darwinism (see Darwinism). The so-called transformed cladists minimize the evolutionary significance of cladograms. A controversial method of classification in which animals and plants are placed into taxonomic groups called clades when they share characteristics (known as homologies) that are thought to indicate common ancestry. It is based on the assumption that two new species are formed suddenly, by splitting from a common ancestor, and not by gradual evolutionary change. A diagram indicating these relationships (called a cladogram) therefore consists of a system of dichotomous branches: each point of branching represents divergence from a common ancestor, as shown in the diagram. Thus the species A to F form a clade as they share the common ancestor X, and species A to D form a clade of a different taxonomic rank, sharing the ancestor X2. Species C to F do not form a clade, since the latter must include all the descendants of a common ancestor. Special taxonomic system, founded by W. Hennig (1966), and applied to the study of evolutionary relationships. It proposes that common origin can be demonstrated by the shared possession of derived characters, characters in any group being either primitive or derived. In the branching diagrams (cladograms) used to portray these relationships, it is assumed that cladogenesis, or splitting of an evolutionary lineage, always creates two equal daughter taxa: the branching is dichotomous. Thus each pair of daughter taxa constitutes a monophyletic group with a common stem taxon, unique to the group, and a parent taxon always gives rise to two daughter taxa which must be given different names from each other and from the parent, so the parent species ceases to exist. A cladogram is therefore synonymous with a classification. A shortcoming of the method would seem to be that usually it takes no account of the time dimension. Syn. cladism.

cladium n. (pl. cladia) A modified, regenerant branch that arises from normal shoots, or thalli and detach readily for vegetative reproductive purposes.

cladocarporus adj. Having the sporophyte terminating a short special fertile branch; somewhat like half-way between acrocarpous and pleurocarpous.

cladocarpous adj. Form of pleurocarp in which sporophytes are borne terminally on short lateral branches; e.g. Fontinalis.

cladode See cladophyll.

cladodia See cladodium.

cladodium (Gr. klados: branchlet, branch) n. (pl. cladodia) Flat leaf like stem. See cladophyll.

cladogenesis (Gr. klados: branchlet, branch; genesis: origin) n. The development of a new clade; the splitting of a single lineage into two distinct lineages; speciation; the derivation of new taxa that occurs through the branching of ancestral lineages, each such split forming two (possibly more) equal sister taxa that are often considered taxonomically separate from the ancestral taxon, though this is no longer considered obligatory.

cladogram (Gr. klados: branchlet, branch; gramma: omething written or drawn) n. A diagram, resulting from a cladistic analysis, which depicts a hypothetical branching sequence of lineages leading to the taxa under consideration. The points of branching within a cladogram are called nodes. All taxa occur at the endpoints of the cladogram.

cladophyll (Gr. klados: branchlet, branch; phyllon: leaf) n. A stem with the form and function of a leaf; a flattened photosynthetic branch assuming the form of and closely resembling an ordinary foliage leaf. Syn. cladode, phylloclade.

cladoptosic adj. Dropping the leaves, branches, and stems at one time, as in Taxodium.

cladoptosis n. Th loss of whole branches or branchlets by abscission at the base. Cf. deciduous.

clambering adj. Weakly climbing on other plants or surrounding objects.

clammy-pubescent adj. With sticky glandular hairs.

clasping adj. Wholly or partly surrounding the stem.

class (L. classis: class, group) n. A major taxonomic rank, between order and phylum or division.

classification (L. classis: class, group) n. Systematic arrangement of hierarchal levels of taxonomy. Any scheme for structuring data that is used to group individuals. In ecological and taxonomic studies numerical classification schemes have been devised, but various hierarchical or non-hierarchical classificatory strategies have also been used. In taxonomy, the fundamental unit is the species. Among living forms species are groups of individuals that look alike and can interbreed, but cannot interbreed with other species. In palaeontology, where breeding capability cannot be determined, species are defined according to morphological similarities. In formal nomenclature, taxonomists follow the binomial system devised by Linnaeus. In this system each species is defined by two names: the generic (referring to the genus) and the specific (referring to the species). Thus various related species may share a common generic name. Genera (singular: genus) may be combined with others to form families, and related families combined into an order. Orders may be combined into classes, and classes into phyla (singular: phylum) or divisions in the case of Metaphyta. For example, the brachiopods comprise some 11 orders split between two classes and these two classes are the major subdivisions of the phylum Brachiopoda. The basic groupings, the phyla, are combined together into kingdoms, e.g. Plantae (the plants) and Animalia (animals). Some workers have tackled the uncertainties arising from subjectivity in classification by using numerical methods. In their view, if enough characters were measured and represented by cluster statistics, the distances between clusters could be used as a measure of difference. Even so, the worker has to decide (subjectively) how best to analyse the measurements, and so objectivity is lost. Other workers emphasize those features shared by organisms that show a hierarchical pattern (see cladistics).

clathrate (L. clatratus: closed with bars) adj. Lattice-like; having thick lateral (adjacent) cell walls and thin surficial walls; relating to or being a compound formed by the inclusion of molecules of one kind in cavities of the crystal lattice of another.

clavarioid adj. Club-like or coral-like fruiting structure

clavate (L. clava: club) adj. Club-shaped; having the form of a club; growing gradually thicker, wider toward the top, as certain parts of a plant; tapering upwards from a narrow base. Syn. claviform.

clavellate adj. Diminutive of clavate.

clavicle (L. clavicula: tendril of vine) n. A tendril.

claviculate (L. clavicula: tendril of vine) adj. With tendrils.

claviform (L. clava: club; forma: shape) See clavate.

claw n. The narrowed, stalk-like base of some sepals, petals or bracts.

clay n. A very fined grained soil that is plastic when moist but hard when fired.

clay loam See clay soil.

clay soil A soil, usually heavy and poorly drained, containing a preponderance of very fine particles. Syn. clay loam.

clayey adj. Abounding in clay.

cleft adj. Divided halfway down to the midrib or further, or generally, any deep lobe or cut.

cleistocarpous (Gr. kleistos: closed; karpos: fruit) adj. Indehiscent; of capsule opening irregularly, not by a lid or valves, e.g., capsule lacking an operculum and annulus or valves and hence opening irregularly. Cf. stegocarpous.

cleistogameon n. A species that reproduces in part, by cleistogamy; apomixis is not present.

cleistogamous (Gr. kleistos: closed; gamos: marriage) adj. Of flowers, self-pollinating and setting fertile seed but never opening. Cf. chasmogamous. Syn. cleistogamous.

cleistogamy (Gr. kleistos: closed; gamos: marriage) n. The condition of having flowers which never open and self-pollination occurs, and the flowers are often small and inconspicuous.

cleistogene (Gr. kleistos: closed; genea: what is generated) n. A plant which bears cleistogamous flowers.

cleistogenous (Gr. kleistos: closed; genea: what is generated) See cleistogamous.

cleistogeny (Gr. kleistos: closed; genea: what is generated) See cleistogamy.

cleistothecia See cleistothecium.

cleistothecium (Gr. kleistos: closed; thŕkŕ: box) n. (pl. cleistothecia) In certain ascomycetous fungi, a closed, globose ascocarp from which the ascopores are released only by its rupture or decay. Syn. clistothecium.

climax n. The culminating stage in plant succession for a given environment, the vegetation being conceived as having reached a highly stable condition. The relatively stable stage or community attained by an available population of organisms in a given environment, often constituting the culminating development in a natural succession or being one of the transitory stable states through which many populations pass before attaining such culmination development.

climax community See climax stage.

climax species The most shade-tolerant species to establish in the process of forest succession. The seedlings of climax species can grow in the shade of the parent trees, ensuring their dominance indefinitely. A disturbance such as fire may kill the climax species, allowing pioneer or earlier successional species to re-establish for a time. Plant species that will remain essentially unchanged in terms of species composition for as long as the site remains undisturbed.

climax stage The ultimate stage in the process of succession, occurring when a plant's ecosystem has reached a point of stability. Also climax community.

climber n. A plant that can climb given support.

climbing adj. Growing more or less erect by leaning or twining on another structure for support.

clinal adj. See cline.

clinandria See clinandrium.

clinandrium (Gr. klinŕ: bed; anŕr, andros: male) n. (pl. clinandria) The portion of an orchid column in which the anther is concealed. Syn. androclinium.

clinanthia See clinanthium.

clinanthium (Gr. klinŕ: bed; anthos: flower) n. (pl. clinanthia) The inflorescence receptacle in the Compositae (Asteraceae). Syn. clinanthus, clinium.

clinanthus See clinanthium.

cline n. A gradual morphological or physiological change in a group of related organisms across their range, usually correlated to environmental or geographic transition; a continuous serie.

clinia See clinium.

clinium n. (pl. clinia) See clinanthium.

clipeiform (L. clypeus: shield; forma: shape) See clypeate.

clistothecia See clistothecium.

clistothecium n. (pl. clistothecia) See cleistothecium.

clockwise adj. Of the direction of twining, the stem taking an ascending clockwise course when viewed from above.

clonal adj. See clone.

clonal varieties They consist of one clone or several closely similar clones propagated by asexual means, such as cuttings, tubers, corms, bulbs , rhizomes, divisions, grafts, or seed produced by obligate apomixis. Examples: `Meyer' zoysiagrass, `Elberta' peach, `Russet Burbank' potato, `Coastal' bermudagrass, `Peace' rose, `Iceberg' chrysanthemum. Examples of obligate apomicts: `Troyer' citrange (rootstock), `Higgins' buffelgrass.

clone (Gr. klon: shoot) n. A group of cells, an organism, or a population of organisms arising from a single ancestral cell. All members of a particular clone are genetically identical. In nature clones are produced by asexual reproduction, for example by the formation of bulbs and tubers in plants or by parthenogenesis in certain animals. New techniques of cell manipulation and tissue culture have enabled the cloning of many plants and some animals. A wide range of commercially important plant species, including potatoes, tulips, and certain forest trees, are now cloned by micropropagation, resulting in more uniform crops. Cloning in animals is more complex, but has been accomplished successfully in sheep and cattle. The first mammal ever to be cloned experimentally from the body cell of an adult was a sheep ('Dolly') born in 1997 after over 200 previous failed attempts. The nucleus containing DNA was extracted from an udder cell (which had been deprived of nutrients) and inserted into an 'empty' egg cell (from which the nucleus had been removed). This reconstituted egg cell was then stimulated to divide by an electric shock and implanted into the uterus of a surrogate mother ewe, who subsequently gave birth to a clone of the original sheep. This breakthrough offers the prospect of producing exact replicas of animals with certain genetically engineered traits, for example to manufacture drugs in their milk or provide organs for human transplantation. A group of plants all originating by vegetative propagation from a single plant, and therefore genetically identical to it and to one another. The aggregate of the asexually produced progeny of an individual; also: a group of replicas of all or part of a macromolecule (as DNA or an antibody); an individual grown from a single somatic cell of its parent and genetically identical to it.

closed adj. Said of a leaf sheath, one which forms an uninterrupted cylinder around the stem.

clouded adj. Blended with patches of another color.

cloud forest A mountain forest covered by a persistent mist that created stunted trees and abundant epiphytes.

clump n. Group; cushion-like growth.

clump-forming adj. Describing a plant which reproduces vegetavely, forming smaller crowns around the parent which can be divided and planted in new locations.

cluster n. A number of similar individuals that occur together. To collect into a cluster.

clustered See cluster.

clypeate (L. clypeus: shield) adj. Shaped like a round shield or buckler; almost the same as scutate. Syn. clipeiform.

coadjuvant See adjuvant.

coadunate (L. coadunare: to reunite) adj. United by growth; closely joined; grown together; united.

coagulant n. An agent that causes a liquid or sol to coagulate.

coal n. A general name given to stratified accumulations of carbon-rich material derived from vegetation. The starting point for coal formation is ususally peat or some similar accumulation of partially decayed plant matter. By the process of compaction, heating, and chemical alteration, the peat is converted by a series of stages into coal. The type of coalification corresponds to the amount of heating that a peat has undergone : peat, lignite (brown coal), bituminous coal, anthracite.

coalesce (L. coalescere: to grow together) v. To grow together or into one body.

coalescence (L. coalescere: to grow together) n. The state or condition of being coalescent; fusing together; union of like parts. See coalesce. Cf. connate, adnate.

coalescent (L. coalescere: to grow together) adj. United together to form a single unit.

coarctate (L. coarctus: pressed) adj. Densely pressed together.

coarse-toothed n. With large teeth; dentate, serrate.

coat n. The covering of a seed; the outer covering of an organ or structure.

cobblestone n. A naturally rounded stone larger than a pebble and smaller than a boulder; especially such a stone used in paving a street or in construction.

cocarcinogenin See cocarcinogenins.

cocarcinogenins n. Phorbol ester diterpenes, a type of carcinogen that promotes neoplastic growth only after its initiation by another substance.

cocci See coccus.

coccoid adj. Saif of cells, globose or subglobose, usually free from one another and often grouped within a gelatinous matrix

coccus (Gr. kokkos: grain, seed) n. (pl. cocci) A one-carpel unit of a schizocarp or lobed fruit. One of the (usually 1-seeded) lobes of a distinctly lobed fruit, becoming separate at maturity. Also cocous.

cochlear (Gr. kokhlias: priralled shell, snail) adj. Coiled like a snail-shell; of the arrangement of corolla lobes in a bud, a variant of imbricate aestivation, one petal with both its edges outside those of the adjacent petals, one with the two edges both inside, and the other petals with one edge outside and the other inside. Also cochleate.

cochleariform (Gr. kokhlias: priralled shell, snail; L. forma: shape) adj. Rounded and concave like a spoon or ladle, shaped like the bowl of a spoon; e.g. the leaves of Weymouthia.

cochleate (Gr. kokhlias: priralled shell, snail) adj. Coiled, shaped like a snail-shell. See cochlear.

cocous See coccus.

Codes of Nomenclature The general rules for the assignment of scientific names to taxa.

co-dominance n. The condition that arises when both alleles in a heterozygous organism are dominant and are fully expressed in the phenotype. For example, the human blood group AB is the result of two alleles, A and B, both being expressed. A is not dominant to B, nor vice versa. Cf. incomplete dominance.

coenocytic adj. Of a non-septate multinucleate mass of protoplasm.

coefficient of association A mathematical statement of the frequency of occurrence together of two species not due merely to chance, calculated by dividing the number of samples in which both occur by the number of samples in which it would be expected they both would occur.

coelocaule n. A specialized shoot calyptra in certain leafy liverworts, characterized by extreme axial growth and elongation simulating complete penetration of the sporophyte into the shoot apex; frequently associated with the absence of a perianth; e.g. Trichocolea.

coelospermous (Gr. koilos: hollow; sperma: seed) adj. Hollow-seeded; with the seeds or seed-like carpels hollowed on one side.

coenocarpia See coenocarpium.

coenocarpium (Gr. koinos: common; karpos: fruit) n. (pl. coenocarpia) A fruit formed from an entire inflorescence, as in the fig or pineapple; a syconium or multiple fruit.

coenocarpous asd. Same as syncarpous.

coenocyte (Gr. koinos: common; kytos: what covers) n. An organism made up of a multinucleate, continuous mass of protoplasm enclosed by one cell wall, as in some algae and fungi.

coensorus n. In ferns, the extension of a sorus, or united sori that appear to be a single sorus.

coerulean (L. c­rulus: blue) adj. Blue or bluish. Syn. caerulescent, coerulean.

coerulescent See coerulean.

coetaneous (L. cum: with; Štas: age, time) adj. With the leaves and flowers developing at the same time

coflorescence n. The cluster of flowers that terminates a lateral branch of a synflorescence.

coherent (L. cohŠrere, to be tied together) adj. Having parts united, having cohesion. Referring to parts that are usually separate but have become fused together, such as petals in a floral tube. Having similar parts or organs in contact with one another but not fused. Cf. adherent.

cohering (L. cohŠrere, to be tied together, to stick tigether) adj. Sticking togother, united.

cohesion (L. cohŠrere, to be tied together, to stick tigether) n. The ticking together of floral parts of the same whorl without organic fusion. The attachment is not as firm or solid as connate.

colchicine n. An alkaloid derived from the autumn crocus, Colchicum autumnale. It inhibits spindle formation in cells during mitosis so that chromosomes cannot separate during anaphase, thus inducing multiple sets of chromosomes (see polyploid). Colchicine is used in genetics, cytology, and plant breeding research and also in cancer therapy to inhibit cell division.

colchiploid adj., n. (Of) the Colchicine-induced polyploid.

coleoptile (Gr. koleos; sheath; ptilon: soft feather, down) n. The first leaf above the groud, forming a sheat around the stem tip, in grasses; the sheath protecting the stem tip in monocotyledons.

coleorhiza (Gr. koleos; sheath; riza: root) n. The sheath which surrounds and is penetrated by the radicle in some seeds.

collagen (Gr. kolla: gum, glue; genea: what is generated) n. Long proteins whose structure is wound into a triple helix. The resulting fibers have a high tensile strength. Collagen is a primary component of mammalian hair.

collar n. Region of junction between blade and leaf sheath of grasses.

collared branch See gyrothecal.

collateral (L. cum: with; lateralis: of the side) adj. Situated side by side; adjacent and on the same radius of an axis.

collecting permits Papers granting permission to collect specimens of flora of parks, nature preserves, foreign countries, or other protected areas.

collection bottles Glass or plastic bottles with waterproof screw tops or vial type bottles, used to collect specimens such as pollen, buds, bark, seeds, insects, etc.

collenchyma (Gr. kolla: glue; enkhuma: infusion) n. Living, supportive tissue with chloroplasts generally just beneath the surface consisting or more or less elongated cells usually thickened unevenly in a manner somewhat variable in different groups of plants.

collenchymatous adj. With cell walls more heavily thickened at the angles; e.g. in bryophytes these thickening are restricted to leaf cell angles. See collenchyma.

collet n. The junction, sometimes marked by an external line, between the radicle and hypocotyl in the embryo or seedling.

colleter n. A glandular hair, often an obviously mucilaginous secretory hair, not vascularised, commonly found in groups or tufts near or at the adaxial base of the leaf and on the calyx.

collicula n. (pl. colliculae) A small, rounded or hillock-like elevation. Syn. colliculus

colliculae See collicula.

colliculate adj. Covered with small, rounded or hillock-like elevations.

colliculi See colliculus.

colliculus n. (pl. colliculi) A small elevation, as on the surface of the optic lobe of the brain. Syn. collicula.

collum n. (pl. colla) The neck or tapering base of the capsule; archaic word for capsule neck.

colluvia See colluvium

colluvial adj. See colluvium

colluvium n. (pl. colluviums or colluvia) A loose deposit of rock debris accumulated through the action of gravity at the base of a cliff or slope

colonial adj. Usually used to describe cloning by vegetative reproduction, the seemingly separate plants having arisen from rhizomes, stolons, or roots of a single or of neighboring 'parent' plants.

colony n. A stand, group, or population of neighboring plants of one species, the origin having been colonial, from seeds, rhizomes, stolons, etc.

colored (L. color: color) adj. Of some hue, other than green.

colpate adj. Having longitudinal germinal furrows in the exine.

colpi See colpus.

colporate adj. Of a pollen grain, having both an elongated and a rounded aperture. Cf. porate.

colpus n. (pl. colpi) An elongated aperture of a pollen grain with a length to breadth ratio greater than 2. Cf. colporate, porate.

columella (L. columella: little column) n. (pl. columellae) A small columnlike part; an axis; the central axis (of sterile tissue) in the sporogenous region of a moss capsule and in hornworts; sometimes applied to the central axis of fruits and cones.

column (L. columna: column) n. The lower part of an awn in grasses, when distinctly different in form from the upper part; structure in Orchidaceae, Asclepiadaceae and Stylidiaceae, extending above the ovary of a flower and incorporating stigma, style and stamens (gynostemium). The plant structure that supports the lid of a pitcher-plant.

column foot In Orchidaceae, the basal platform to which the lip is attached to the column.

coma (Gr. komŕ: hair, beard) n. (pl. comae) A tuft of soft hairs, as at the apices or bases of seeds; a bunch of branches, the leafy crown of a tree, a cluster of leaves at the end of a stem; a terminal cluster of bracts on a flowering stem, as in pineapples.

comae See coma.

comal (Gr. komŕ: hair, beard) adj. Of or pertaining to a coma.

comal tuft A a tuft of leaves at tip of a stem or branch; e.g. Bryum.

co-management The sharing of authority, responsibility, and benefits among government, businesses, and local communities in the management of natural resources, e.g., cooperation among the National wildflower Research Center, Texas Department of Agriculture, landscape architects, and nurseries in the production of native plants for landscaping.

comate (Gr. komŕ: hair, beard) See comose.

comatose (Gr. komŕ: hair, beard) See comose.

combination n. In taxonomy, the name below the rank of genus, which combines the genus name along with the species and lower ranks, such as subspecies, variety, etc.

combining ability The general combining ability is the average progeny performance of a cultivar in a series of crosses; the specific combining ability is the deviation from the performance predicted from general combining ability. The general combining ability is then the average performance of a strain in a series of crosses. The specific combining ability is then the deviation from performance predicted on the basis of general combining ability.

commensal adj., n. (Of) a plant living with, on, or in another, without injury to either.

commensalism n. An inter-species interaction in which one organism is aided by the interaction and the other is neither benefited nor harmed.

commensality See commensal

commensally See commensal.

commissural (L. commissio: joint) adj. Of or pertaining to a commissure.

commissure (L. commissio: joint) n. A place of joining or meeting, as where one carpel joins another in the Umbelliferae.

common name Identifying term which often reflects appearance, legend, or use of a plant species. It may vary greatly by region, increasing the need for standard binomial nomenclature.

common property resource management The supervision of a specific resource (such as a forest or pasture) by a well-defined group of users with the authority to regulate its use by members and outsiders.

community n. A blended group of species inhabiting a given area; the organisms influence one another's distribution, abundance, and evolution.

comose (Gr. komŕ: hair, beard) adj. Having a tuft of hair; with larger and more crowded leaves forming tufts or comae at the stem tips; e.g. Camplyopus, Bryum. Syn. comate.

compact adj. Pressed together or closely joined; in rhizomes, those with short internodes and closely spaced stipes.

companion cell A specialized cell of phloem, derived from the same parent cell as the closely associated sieve-tube element immediately adjacent to it; the nucleus of the companion cell supports both its own cell and the cell of its associated the sieve-tube element.

competition n. Involves the removal or reduction of some factor from the environment by a plant or group of plants that is sharing the same habitat. Competition can be by an individual or groups of plants of the same or different species. Factors that may be reduced include water, minerals, food, and light.

compitum n. A tract of tissue down the which pollen tubes grow and that is common to all the carpels of the one flower.

complanate (L. complanare: to level) adj. Flattened or compressed, such as leaves flattened into more or less one plane; e.g. Entodon, Erpodium, Plagiothecium.

complementary genes Genes that are similar in phenotypic effect when present separately but react to produce new characters when they are combined; a 9 to 7 ratio results in the F2 if two such genes are complementary for a dominant effect and a 15 to 1 ratio if they are complementary for a recessive effect.Cf. duplicate factors.

complete (L. completus: filled, finished, thorough) adj. With all of the parts typically belonging to it present, as a flower with sepals, petals, stamens, and pistils.

complete flower Having all the principal parts, particularly the stamens and pistils.

complete metamorphosis See holometabolism.

complex (L. complex: united, joined) n. A group of very similar and obviously related plants where it is difficult to find identification limitations, and where the relationships are not fully understood.

complex thallus A multistratose thallus with internal tissue differentiation, usually with air-pores, air-chambers, storage tissue and ventral scales; e.g. Marchantia.

complicate (L. complicatus: rolled, folded) adj. Of leaves, the lamina (or part of the lamina) folded upon itself; folded lengthwise along a keel; e.g. the leaves of Fontinalis antipyretica. See conduplicate.

Compositae n. The largest family of flowering plants, the Compositae (Asteraceae), comprising about 1,100 genera and more than 20,000 species and characterized by many small flowers arranged in a head looking like a single flower and subtended by an involucre of bracts. A head may consist of both ray flowers and disk flowers, as in the sunflower, of disk flowers only, as in the burdock, or of ray flowers only, as in the dandelion.

composite (L. compositus: put together) adj. Belonging to the Compositae (Asteraceae) a family of plants including the daisy, the dandelion, aster, etc., in which the florets are borne in a closed head surrounded by a common involucre of bracts.

composite-cross populations A population generated by hybridizing more than two varieties or lines of normally self-fertilizing plants and propagating successive generations of the segregating population in bulk in specific environments so that natural selection is the principal force acting to produce genetic change; artificial selection may also be imposed on the population, the resulting population is expected to have a continuously changing genetic makeup; breeder seed is not maintained as originally released; Examples: `Harlan' barley, `Mezcla' lima bean.

composite fruit A type of fruit that develops from an inflorescence rather than from a single flower. See pseudocarp; sorosis; strobilus; syconus.

compost n. Decomposed organic maker, usually used to enrich the soil.

compound adj. With two or more like parts in one organ; of a leaf, having the blade divided into two or more distinct leaflets; of an inflorescence, made up of an aggregate of smaller inflorescences.

compound flower head A flower head with outer ray flowers forming "petals" surrounding the inner disc flowers, as in the Asteraceae. (alt. composite flower head).

compound fruit A fruit that is made up of two or more distinct aggregate fruit, e.g. as in many Magnoliales and Rosaceae.

compound leaf A leaf divided into smaller leaflets.

compound pore Air pore bordered by both superficial cells arranged in concentric rings and an internal, cylindrical or barrel-shaped structure of epidermal origin; e.g. Marchantia.

compressed adj. Flattened in one plane, either dorsally (bringing the front and back closer together) or laterally (bringing the sides closer together). Cf. complanate.

compression wood A kind of reaction wood with much-thickened fibers that are round in cross section and produced on the lower or abaxial side of the branch-stem junction; in general, there is more lignin and less cellulose than in normal wood. Cf. tension wood.

concave (L. cum: with; cavus: hollow) adj. Hollowed out or curved inward.

concaulescent adj. Said of axillary branching, when the buds are as if they were shifted up the stem, being borne way above the subtending leaves. Cf. recaulescent.

concavo-concave (L. cum: with; cavus: hollow) adj. Concave on both sides.

concavo-convex (L. cum: with; cavus: hollow; convexus: rounded, arched) adj. Concave on one side and convex on the other.

conceptacle (L. conceptus: the act of containing) A flask-shaped cavity with a small opening (the ostiole) that is found in the swollen tip of certain brown algae, such as Fucus. It contains the sex organs.

concentric adj. Arranged around a common centre.

conchate adj. Shaped like a vivalve shell.

concolored See concolorous.

concolor adj. Of uniform color. Also concolorous.

concolorous (L. cum: with; color: color) adj. Coloured uniformly; the same colour on both sides. Of uniform colour; of leaves, having both surfaces the same colour. Syn. concolored. Cf. discolorous.

concrescent adj. Growing together, especially of parts that were originally separate.

concretion (L. concretus: condensation. thickening) n. The act or process of making or becoming solid.

Condobolinian n. A stage in the Devonian of Australia, underlain by the Cunninghamian, overlain by the Hervyan, and roughly contemporaneous with the Givetian and, possibly, Frasnian Stages of Europe.

conduplicate (L. conduplicatus: doubled) adj. Folded together, with the fold-line along the long axis, e.g. of cotyledons in a seed, as the leaves of many grasses, of the leaves of Eustichia, Fontinalis antipyretica.

conduplicate-flat adj. Said of leaf ptyxis, folded together at an angle of about 90 degrees along the midrib, the sides flat.

conduplicate-involute adj. Dais of leaf ptyxis, folded together at an angle of about 90 degrees along the midrib, the margins incurved.

conduplicate-plicate adj. Said of leaf ptyxis, folded together along the midrib, the two sides folded like a concertina in cross section.

condyle n. The inward projection of the endocarp around which the seed is folded, as in Menispermaceae.

cone (Gr. k˘nos: cone) n. In gymnosperms and club-mosses, a group of sporophylls arranged compactly on a central axis; (loosely) in Casuarina, a woody multiple fruit incorporating the bracts and bracteoles associated with the flowers. A reproductive structure occurring in gymnosperms, known technically as a strobilus. It consists of sporophylls bearing the spore-producing sporangia. Gymnosperms produce different male and female cones. The large woody female cones of pines, firs, and other conifers are made up of structures called ovuliferous scales, which bear the ovules. Cones are also produced by clubmosses and horsetails.

conferted adj. Closely crowded. See also: congested, constipate.

confervoid adj. Formed of fine threads, as green algae; having a loosely interwoven habit; e.g. plants of Platydictya confervoides.

conflorescence (L. cum: with; in; in; florus: flowered) n. A compound inflorescence consisting of two or more unit inflorescences. A flower-bearing branch system in which the main axis does not end in a flower but the axes of the branches do.

confluent adj. Running into each other; blended into one so as to obscure the evidence of union; e.g. margins and costa of Sciaromium.

confused center Of a flower center whose petals are disorganized, not forming a pattern.

congeneric adj. Belonging to the same genus.

congenital adj. Said of fusion of parts from the very beginning of development. Cf. postgenital.

congested adj. Close together. Cf. conferted, constipate.

conglutinate adj. Said of hyphae, especially paraphyses, glued or stuck together.

congregate adj. Growing in dense proximity.

congruent (L. congruens: agreeing, corraborating) adj. Structurally identical in form and size.

conical (Gr. k˘nos: cone) adj. Cone shaped, as the young form of many spruces, as the operculum of Bryum .

conidia See conidium.

conidial adj. See conidium.

conidian adj. See conidium.

conidiogenous adj. Producing conidia.

conidioma n. (pl. conidiomata) A multi-hyphal, conidium-bearing structure. Cf. pycnidium.

conidiomata See conidioma/

conidiophore n. A hypha that bears conidia.

conidiospore n. An exogenous, non-motile vegetative spore.

conidium (Gr. konis: dust) n. (pl. conidia) In fungi, an asexual spore formed by abstriction at the top of a hyphal branch, an asexual spore produced in a pycnidial conidioma.

conifer (L. conus: cone; ferre: to carry) n. A cone-bearing tree of the pine family, usually evergreen; any of an order (Coniferales) of mostly evergreen trees and shrubs including forms (as pines) with true cones and others (as yews) with an arillate fruit. A gymnosperm tree of the widely distributed phylum Coniferophyta (550 species), most abundant in the colder temperate zones, especially in the north; elsewhere they are usually found at high altitudes. Conifers are typically pyramidal in form, with a straight continuously growing stem that can reach great heights (see Sequoia). Nearly all conifers are evergreen (larches are exceptions), with simple needle-like or scalelike leaves. The reproductive organs are typically borne in separate male and female cones, usually on the same tree, and produce winged seeds that are dispersed by wind (the yew and juniper are exceptions). The wood of conifers-called softwood-is economically important, being used for construction and as a source of paper pulp, etc. (see timber). The principal families are the Pinaceae (pines, cedars, spruces, firs, larches, hemlocks, etc.); Cupressaceae (cypresses, junipers, arbor vitae, etc.); Taxodiaceae (sequoias, swamp cypress, etc.); Taxaceae (yews); and Araucariaceae (monkey puzzle, etc.).

Coniferophyta (L. conus: cone; ferre: to carry; Gr. phyton: plant) n. A phylum of seed-bearing plants comprising the conifers, including the pines, firs, and spruces. Conifers have an extensive fossil record going back to the late Devonian. The gametes are carried in male and female cones, fertilization usually being achieved by wind-borne pollen. The ovules and the seeds into which they develop are borne unprotected (rather than enclosed in a carpel, as are those of the Anthophyta). Internal tissue and cell structure of these species is not as advanced as in the angiosperms. Conifers are typically evergreen trees inhabiting cool temperate regions and have leaves reduced to needles or scales. The wood of conifers, which is called softwood in contrast to the hardwood of angiosperm trees, is widely used for timber and pulp. Syn. Pinopsida. See also gymnosperm.

coniferous (L. conus: cone; ferre: to carry) adj. Bearing cones or strobili.

coniine n. A pyridine alkaloid.

conjugate (L. conjugatus: united, married) adj. Coupled together, as the paired leaflets of a pinnate leaf.

conjugation (L. conjugatus: united, married) n. The union of gametes.

connate (L. connatus: born with) adj. Congenitally united, fused to another organ (or other organs) of the same kind. Cf. adnate, coalescent, adherent.

connate-perfoliate (L. connatus: born with; per: through; folium: leaf) adj. Where opposite leaves are completely joined at the bases, leaving the appearance that the stem pierces through.

connective (L. connectere: to tie) n. The portion of the stamen connecting the two pollen sacs of an anther. The part of an anther that connects the lobes.

connivent adj. Approximate but not organically united; converging; arching over so as to meet, coming into contact; converging, but not actually fused or united; directed or pointing together, though not fused, as the tips of leaf lobes inclined and converging towards one another.

conocarp (Gr. konos: cone; karpos: fruit) n. A composite fruit of many carpels on a conical receptacle, as the strawberry. Syn. conocarpium.

conocarpia See conocarpium.

conocarpium n. (pl. conocarpia) See conocarp.

conocarpous (Gr. k˘nos: cone; karpos: fruit) adj. With a conic fruit.

conoidal (Gr. k˘nos: cone) adj. Imperfectly conical.

conopodia See conopodium..

conopodium (Gr. k˘nos: cone; pous, podos: foot) n. (pl. conopodia) A conical receptacle.

conservation n. A careful preservation and protection of something, especially the planned management of a natural resource to prevent exploitation, destruction, or neglect.

conservation lists Recommended protection lists of endangered, threatened, and protected plants, giving information from groups other than those with enforcement powers.

conservation of names An International botanical Congress may decide to conserve (retain as valid and accepted) what has been decided to be an illegitimate name; the measure provides that highly familiar names not get lost in synonymy.

consimilar (L. cum: with; similis: same) adj. Similar to one another.

conspecificity n. About subspecies belonging to the same species.

conspecific (L. cum: with; species: species) adj. Of the same species.

conspicuous (L. conspicuus: visible, easily seen) adj. Easily visible without a lens, often extended to mean showy or prominent.

constipate (L. constipare: to press, tighten) adj. Crowded together.

constricted (constrictus: tightened, dense, compact) adj. Drawn together or abruptly narrowed; tightened; of varying width; e.g. the urn below the capsule mouth in Sematophyllum, Anacamptodon splachnoides.

consumption n. A progressive wasting of body tissue. Pulmonary tuberculosis (no longer in scientific use in this last meaning).

consumptive adj.; n. Of, relating to, or afflicted with consumption. A person afflicted with consumption.

contiguous (L. contiguus: touching) adj. Adjoining; touching, but not fused.

continuous (L. continuus: continuous) adj. Not jointed; not separating at maturity along a well-defined line of dehiscence; the touching of similar or dissimilar parts without fusion; i.e. leaves so arranged on the stem that there is neither overlapping nor a clear space between them.

contort See contorted.

contorted (L. contortus: twisted, twined) adj. Twisted or bent; irregularly curved; convolute; a variant of imbricate aestivation, e.g. of a corolla, in which each segment has one edge overlapping the adjacent segment, like a furled umbrella. Also contort. Cf. tortuose.

contortiplicate adj. Said of a variant of imbricate aestivation, e.g. of a corolla, in which each segment has one edge overlapping the adjacent segment, like a furled umbrella, but the corolla is connate.

contracted (L. contractus: tightened, narrow) adj. Narrowed; narrow, thick, and dense, as an inflorescence with crowded, short or appressed branches.

contractile roots Roots that can shorten themselves much like a worm does, drawing the plant down deeper into the soil. They usually have a wrinkled surface for expanding and contracting.

convergence n. Similarities which have arisen independently in two or more organisms that are not closely related; the independent development of similar (analogous) structures in different groups; convergent evolution is thought to be the result of similar environmental selection pressures on different groups. Contrast with homology. Same as homoplasy.

convergent adj. Meeting together as leaf veins which come together at the leaf apex.

convergent evolution See convergence.

convex (L. convexus: rounded, curved) adj. Rounded and curved outward on the surface.

convolute (L. convolutus: rolled around, wrapped) adj. Said of parts rolled or twisted together when in an undeveloped stage, as in some corollas in the bud stage, a form of imbricate aestivation in which each segment has one edge overlapping the adjacent segment, like a furled umbrella; rolled together and forming a sheath; e.g. perichaetial leaves of Holomitrium.

cooperation (L. cooperatio: cooperation) An association between two or more members of the same species (intraspecific cooperation), or between individuals of different species (interspecific cooperation), in which all members benefit. An example of interspecific cooperation is the relationship formed between ants and aphids: the aphids gain protection by living in the ant colonies, while the ants feed on secretions from the aphids. Interspecific cooperation is a looser association than mutualism.

copious (L. copiosus: plentiful) adj. Large in number or quantity; abundant.

copolymer (L. cum: with; Gr. polys: many; meros: part) n. A polymer manufactured from two or more different monomers. Acrylic fibres for example are made by copolymerization of ethene derivatives such as propenenitrile, CH2CHCN. Butadiene forms two important copolymers SBR and ABS.

coppice n. A thicket of bushes or small trees; sprouts arising from a stump. Syn. copse.

copse n. A thicket of bushes or small trees; woods. Syn. coppice.

coracoid (Gr. korax: raven; eid˘: to look like) adj. Shaped like the beak of a crow.

coralloid (Gr. korallion: coral; eid˘: to look like) adj. Coral-like; often brittle; often said of isidia. Syn. coralloidal.

coralloidal See coralloid.

cord n. A dense strand of hyphae.

Cordaitales n. An order of extinct gymnosperm trees that-with Calamites formed vast forests during the Carboniferous and Permian periods (370-240 million years ago); coal was formed from their fossilized remains. The trees probably grew up to 30 m high, with a tall columnar trunk and strap-shaped leaves, up to 1 m long.

cordate (L. cor, cordis: heart) adj. Heart-shaped (in the traditional playing-card sense), with the notch at the base. With a sinus and rounded lobes at the base, the overall outline usually ovate; often restricted to the base rather than to the outline of the entire organ; e.g. Calliergon. Cf. auriculate.

cordiform (L. cor, cordis: heart; forma: shape) adj. Shaped like a heart (in three dimensions). See cordate.

coreaceous See coriaceous.

coriaceous (L. coriaceus: leathern) adj. Leathery; tough; resembling leather. Syn. coreaceous, corious.

corious See coriaceous.

cork n. A protective layer of tissue, elastic in texture with air-filled outer cells.

cork cambium A narrow cylindrical sheath of meristematic cells that produces cork cells to replace the epidermis during secondary growth (growth in width).

corky See cork.

corm (Gr. kormos: piece [of wood]) n. A fleshy, underground organ often rounded in shape but of no distinct characteristic shape or size in some species, formed by certain plants, e.g. crocus and gladiolus; it is filled with nutrients, is composed of two or more internodes and covered externally by a few thin membranous scales or cataphyllary leaves; it acts as a vegetative reproductive structure, and enables a plant to survive from one growing season to the next; it is actually a short swollen food-storing stem surrounded by protective scale leaves; one or more buds in the axils of scale leaves produce new foliage leaves and flowers in the subsequent season, using up the food stored in the stem. Cf. bulb.

cormatose (Gr. kormos: piece [of wood]) See cormous.

cormel (Gr. kormos: piece [of wood]) n. A small or secondary corm produced by a larger corm, that develops at the base of the mother corm. Alt. cormlet.

cormlet See cormel. (Gr. kormos: piece [of wood])

cormoid (Gr. kormos: piece [of wood]; eid˘: to be like) adj. Corm-like.

Cormophyta (Gr. kormos: piece [of wood]; phyton: plant) n. In older classifications, a division comprising all plants that have a stem and root.

cormophyte (Gr. kormos: piece [of wood]; phyton: plant) n. A plant of the former botanical division Cormophyta, having a stem and root system.

cormous (Gr. kormos: piece [of wood]) adj. Bearing corms.

corneous (L. corneus: horny) adj. Consisting of a horny substance; horny.

cornet (L. cornu: horn) n. A horn-like structure.

corniculate (L. corniculum: ittle horn) adj. With small horn-like protuberances. Syn. proboscidate.

cornoside n. A compounds that occur in taxa where there are no iridoids, even though

cornucopiate adj. Shaped like a cornucopia or horn.

cornute (L. cornu: horn) adj. Horned. Syn. cornuted.

cornuted See cornute.

corolla (L. corolla: little crown, garland) n. The petals of a flower, collectively, forming the inner whorl or whorls of the perianth, usually colored or otherwise differentiated; the corolla encircles the stamens and carpels; its form is very variable; the petals may either be free (polypetalous) or united to form a tube (gamopetalous or sympetalous).

corollaceous (L. corolla: little crown, garland) adj. Of, pertaining to, or ressembling a corolla.

corollate (L. corolla: little crown, garland) adj. Having a corolla. Syn corollated.

corollated See corollate.

corolline corona Fleshy ridges or outgrowths of tissue attached to the corolla tube.

corona (L. corona: crown) n. A ring of tissue arising from the corolla or perianth of a flower and standing between the perianth lobes and the stamens, as in the narcissus.

coroniform (L. corona: crown; forma: shape) adj. Shaped like a crown.

corpusculum (L. corpusculum: little body) n. A gland associated with the pollinium in the Asclepiadaceae.

corrugate See corrugated.

corrugated (L. corrugatus: wrinkled) adj. Wrinkled or folded into alternating furrows and ridges; regularly wavy. Also corrugate. Cf. rugose, undulate.

corrugation (L. corrugatus: wrinkled) n. A wrinkle, fold, furrow, or ridge.

cortex (L. cortex: bark, rind, shell, husk) n. (pl. cortices) In rhizomes and other axes, the tissue between the stele and the epidermis; in lichens, the outermost layer of the thallus; in seaweeds and fungi the tissue external to the central tissue of longitudinal cells; in plants, the typically parenchymatous layer of tissue external to the vascular tissue and internal to the corky or epidermal tissues of a green plant; broadly: all tissues external to the xylem; in bryophytes, the stem tissue located between the central strand and epidermis, either of which may not be differentiated; often used in liverworts to denote the differentiated outer rind or epidermal cell layer of the stem; in lichens, the outermost layer of the thallus which, if present, consists of compacted hyphae which may appear either fibrous or cellular. Cf. epidermis, medulla.

cortical (L. cortex, corticis: bark, rind, shell, husk) adj. Of or pertaining or relating to the cortex.

corticate (L. cortex, corticis: bark, rind, shell, husk) adj. Having a cortex.

corticioid adj. Of the flat fruiting body of the Basidiomycota which develops directly on the substrate with the hymenium on the outer side.

Corticium n. A genus of fungi.

corticolous adj. Growing on the woody parts of trees and shrubs.

cortina n. A web-like or silky veil extending from the cap margin to the stem in young mushrooms of certain species, soon disappearing or leaving remnants on stem or cap margin.

cortinate adj. With a cortina, weblike.

corymb (Gr. korymbos: flower cluster) n. A racemose inflorescence in which the lower flower stalks are longer than the higher ones, i.e. the lower pedicels are successively elongated, resulting in a flat-topped cluster of flowers, the outer flowers opening before the inner; e.g. Viburnum.

corymbiform (Gr. korymbos: flower cluster; L. forma: shape) adj. Of an inflorescence with the general appearance, but not necessarily the structure, of a true corymb.

corymbose (Gr. korymbos: flower cluster) adj. Having flowers in corymbs; corymblike (the term is sometimes used in the same sense as corymbiform).

cosmopolitan (Gr. kosmos: world; politŕs: citizen) adj. Widely distributed over the globe.

costa (L. costa: rib, side) n. (pl. costae) A rib or prominent mid-vein; a midrib or mid-nerve of a pinna or moss leaf.

costae See costa.

costapalmate (L. costa: rib; palmatus: stamped with the shape of a hand) n. Ribbed or veined palmately.

costate (L. costa: rib, side.) adj. Having a costa; ribbed; having one or more longitudinal ribs or nerves.

costulate adj. Having costulae, especially in parallel rows.

costular (L. costula: little rib) adj. Pertaining to the ribs or veins.

costule (L. costula: little rib) n. An axis that is a branch of a costa or another costule.

cotyledon (Gr. kotylŕdon: cavity, hollow) n. The first leaf or leaves of a seed plant, found in the embryo of the seed which may form the first photosynthetic leaves or may remain below ground. A part of the embryo in a seed plant. The number of cotyledons is an important feature in classifying plants. Among the flowering plants, the class known as Monocotyledonae have a single cotyledon and Dicotyledonae have two. Conifers have either two cotyledons, as in Taxus (yews), or five to ten, as in Pinus (pines). In seeds without an endosperm, e.g. garden pea and broad bean, the cotyledons store food, which is used in germination. In seeds showing epigeal germination, e.g. runner bean, they emerge above the soil surface and become the first photosynthetic leaves.

cotyliform (Gr. kotylŕ: cavity, little cup) adj. Cup-shaped; rotate, but with an erect limb.

cotype n. An additional type herbarium specimen from which the taxon is described. A term formerly used for syntype and sometimes (erroneously) for isotype and paratype. This is an old term that was used loosely and is not used by today 's taxonomists.

coumarin n. A lactone of phenylpropanoic acids with a H-benzopyran-one nucleus, occuring as glycosides, sometimes located in secretory ducts called vittae, produce the characteristic new-mown hay smell of many grasses.

coumestan See coumestans.

coumestans n. A class of flavonoids derived from isoflavones, which have a coumarin structure.

counteradaptation Reciprocal acclimation of two or more species to each other over a period of time.

counterclockwise adj. Said of the direction of twining, the stem taking an ascending counterclockwise course when viewed from above.

counterirritant adj., n. (Of) herbal preparations that produce irritation when applied locally to stimulate circulation in the area of another irritated area.

coupling n. Said when linked recessive alleles occur in one homologous chromosome and their dominant alternatives occur in the other chromosome; opposed to repulsion in which one dominant and one recessive occur in each member of the pair of homologous chromosome.

Couvinian See Eifelian.

cpDNA See chloroplast DNA.

crampon n. An adventitious root serving as a support, as in ivy.

craspedodromous adj. Said of pinnate venation in which the secondary veins terminate at the margins, often as teeth.

crassinucellar See crassinucellate.

crassinucellate Of an ovule with one or more layers of cells outside the embryo sac but distinct from the epidpermis of the ovule. Also crassinucellar.

crateriform (L. crater: vase) adj. Bowl-shaped, goblet-shaped.

creeper n. A plant running along at or near the surface of the ground and rooting. See also creeping.

creeping adj. Growing along the surface of the ground, or just beneath the surface, and producing roots, usually at the nodes.

cremocarp (Gr. kremas: hanging; karpos:fruit) n. A dry fruit that is a type of schizocarp formed from two one-seeded carpels. The carpels remain separate and form indehiscent mericarps that are attached to a central supporting strand (carpophore) for some time before dispersal. It is characteristic of the Umbelliferae (Apiaceae; carrot, fennel, parsnip and the like family). See schizocarp.

Crenarchaeota n. The less derived (see Apomorph) of the two kingdoms of the Archaea, composed principally of extreme thermophiles and psychrophiles. Members of the Crenarchaeota show a greater genetic similarity to those belonging to the domains Eucaryota and Bacteria than do those of the Euryarchaeota.

crenate adj. With small, rounded, convex-sided teeth on the margin. Having a notched, indented, or scalloped edge, as certain leaves; scalloped. Also : crenated.

crenated See crenate.

crenation n. A rounded projection or tooth along the margin of a leaf.

crenophilous adj. Thriving in springs.

crenulate adj. Minutely crenate, minutely scalloped; having very small rounded teeth (subjectively distinct from crenate). Syn. crenulated.

crenulated See crenulate.

crenulation n. A very small rounded tooth along a margin; a minute crenation.

creosote (Gr. kreas. kre˘s: flesh; s˘ter: which protects) n. An oily liquid with a strong, penetrating odor, obtained by the distillation of wood tar, and used as a preservatiev and an antiseptic.

crescentic (L. crescere: to grow) adj. Crescent-shaped.

crest (L. crista: crest, feather) n. An elevated ridge or rib on a surface; a tuft of short, stiff hairs.

crested (L. crista: crest, feather) adj. With a crest, usually on the back or at the summit.

cretaceous (L. creta: chalk) adj. Chalky.

Cretaceous (L. creta: chalk) n. Third of the three periods included in the Mesozoic Era. It began approximately 145.6 million years ago and ended about 65 million years ago. It is noted for the deposition of the chalk of the White Cliffs of Dover, England, and for the mass extinction of many invertebrate and vertebrate stocks. Among these were the dinosaurs, mosasaurs, ichthyosaurs, and plesiosaurs.

cribose adj. Of peristome teeth finely perforated with small apertures; e.g. the peristome teeth of Grimmia. Also cribriform.

cribriform (L. cribrum: sieve; forma: shape) adj. Sieve-like. Syn. cribrose, cribrous.

cribrose See cribriform.

cribrous See cribriform.

crinite (L. crinitus: who has long hair, many hair) adj. With tufts of long, soft hairs.

crinkled adj. Flattened and somewhat twisted, kinked, or curled.

crinoid adj. Like a lily.

crinose (L. crinis: hair) adj. Hairy.

crispate (L. crispus: frizzy, curly) adj. Frizzled, curled and twisted in various ways; e.g. in the manner of parsley.

crisped (L. crispus: frizzy, curly) adj. Curly-edged, wavy, as in some fern fronds; often used more loosely to mean variously curled, twisted and contorted; of a margin crumpled or thrown into waves.

cristarque cells Sclereids, the lignin deposited excentrically in a U-shape, that also contain a druse.

cristate (L. crista: crest) adj. With a terminal tuft or crest; in the form of a crest; irregularly notched.

cristulate (L. cristula: little crest; little feather) adj. With a small terminal tuft or crest.

crosier n. The curled top of a young fern frond. The hook of an ascogenous hypha before ascus development Also crozier.

cross n. The offspring of two parents of different species or varieties; a hybrid. Syn. crossbreed. v. To crossbreed or cross-fertilize (plants or animals).

crossbreed See cross.

cross-fertilization n. Fertilization by the joining of gametes from different individuals of the same species (cross-pollination), or from different species (hybridization).

cross-pollinated See cross-pollination.

cross-pollination n. The transfer of pollen from the anther of the flower of one plant to the flowers of a different plant.

cross pollination Pollination of one plant by another.

crossing over The exchange of corresponding segments between chromatids of paired (homologous) chromosomes; it is a process inferred cytologically from new associations of parts of chromosomes, both of which may be observed in an exchange of factors and in combinations of factors differing from those that came in with the parents; the term `genetic cross-over' may be applied to these new gene combinations; its genetic consequence is the recombination of linked genes. Cf. Recombination.

cross-over unit An exchange frequency of 1% between two pairs of linked genes.

crotch n. The angle formed between two joining branches.

croup n. A group of respiratory diseases that often affect infants and children under age 6. It is characterized by a barking cough; a whistling, obstructive sound (stridor) as the child breathes in; and hoarseness due to obstruction in the region of the larynx. It may be mild, moderate or severe, and severe cases, with breathing difficulty, can be fatal if not treated in a hospital.

crown n. That part of a stem at or just below the surface of the ground, where roots join the stem; an inner appendage of a petal or the throat of a corolla; an appendage or extrusion standing between the corolla and stamens, or on the corolla; an outgrowth of the staminal part or circle as in milkweeds; in trees, the branches, twigs, and leaves that form the top of a tree; in roses, the region of the bud union, the point near soil level where the top variety and the understock are joined; a corona.

crown gall Galls on shoots or roots of shrubs, especially those of the rose family, caused by soil bacteria.

crown group All the taxa descended from a major cladogenesis event, recognized by possessing the clade's synapomorphy. See: stem group.

crownshaft n. An apparent extension of the bole in some Palmae, formed by overlapping and sheathing bases of the leaves.

crozier See crosier.

cruciate (L. crux: cross) adj. Cross-shaped; e.g., the four setae initials formed by two divisions of a single cell, the second division at right angles to the first, thus yielding at maturity a seta composed of four distinct cellular clusters in the form of a cross, when viewed in transverse section. See cruciform.

cruciferous adj. Said of stomata, same as anisocytic.

cruciform (L. crux: cross; froma: shape) adj. Cross-shaped.

Crudinian n. The basal stage in the Devonian of Australia, underlain by the Silurian, overlain by the Merionsian, and roughly contemporaneous with the Gedinnian Stage in Europe.

crumpled adj. Said of the vernation of petals in particular, when they are all crumpled in bud, unlike the normal gradually curving arrangement; although the following are strictly speaking not alternatives (i.e. crumpled petals could also be contorted).

crustaceous adj. Brittle and dry; having a hard shell; of marine algae, encrusted with c alcium carbonate.

crustose adj. Hard and brittle. Cust-like, used for lichens having a thallus stretched over and firmly fixed to the substratum by the whole of the lower surface, such thalli generally lack rhizines and a lower cortex.

crymocolous adj. Growing in tundra or polar region.

cryptanthous (Gr. kryptos: hidden; anthos: flower) adj. With the flower hidden; cleistogamous

cryptocotylar adj. Said of germination, when the cotyledons are not exposed and photosynthetic.

cryptogam (Gr. kryptos: hidden; gamos: marriage) n. A general name for plants, and plant-like organisms, that lack flowers, whose sexual reproductive parts then are not conspicuous, and are not reproduced by seeds, i.e. a plant that produces spores, not seeds, in its sexual reproductive cycle, e.g. ferns, mosses, fungi and algae. Cf. phanerogam. Syn. cryptophyte.

cryptogamic adj. See cryptogam.

cryptogamous adj. See cryptogam.

cryptolecanorine adj. Said of an ascoma, with a reduced or inapparent thalline margin.

cryptophyte (Gr. kryptos: hidden; phyton: plant) A plant thta form its reproductive structures, as corms or bulbs, underground or underwater.

cryptopore adj., n. A stoma which is immersedi; having immersed stomata, with the guard cells sunken below level of the exothecial cells and often more or less covered by them. Cf. phaneropore.

C-shaped papilla Papilla (or mammilla) appearing crescent-shaped (occasionally circular) when viewed from above; such papillae may themselves be smooth or rough and variously interlinked, but are typically arranged in groups with the open ends facing inwards; e.g., Encalypta, Phascum, Pottia; also called hob-nail papillae.

ctenoid (Gr. kteis, ktenos: comb; eid˘: to look like) adj. Comblike; rough-edge. See pectinate.

cucullate (L. cucullatus: hooded) adj. Hooded; hood-shaped; a calyptra split along one side only; also used to describe leaves strongly concave and erect or inflexed at the tips, like a monk's cowl; e.g. Aloinella. Syn. cucullated.

cucullate calyptra In mosses, a calyptra that is hood-shaped and split on one side only.

cucullated See cucullate.

cucullately See cucullate.

cucullus (L. cucullus: hood) n. A hood; a seed covering external to the seed coat.

cucumiform Shaped like a cucumber.

cucurbitacin n. A triterpenoid, sometimes coloured, bitter in taste.

cucurbitoid adj. Said a leaf tooth in which there is a translucent apical pad of densely packed cells, the two lateral veins either fusing or connivent with the apical vein.

culm (L. culmus: a stalk, stem) n. The stalk or stem for such plants as grasses and sedges, usually jointed and hollow.

cultigen Plant or group of plants known only in cultivation; presumed to have originated under domestication.

cultivar n. A unvarying variety of plant produced by selective hybridization and maintained by vegetative propagation or by inbred seed; abbreviated cv. A term contracted from `cultivated variety' defined under the International Code of Nomenclature of Cultivated Plants (1969) as `an assemblage of cultivated plants which is clearly distinguished by any characters (morphological, physiological, cytological, chemical, or others), and which, when reproduced (sexually or asexually), retains its distinguishing characters.' This term is essentially different from the concept of botanical variety, which is always in the Latin form prescribed by the International Code of Botanical Nomenclature. These plants are named at three main levels: Genus, species, and cultivar, of which the first two are governed by the Botanical Code and the last is a `fancy name' in a modern language with capital initial letters and distinguished clearly from the botanical name or accepted common name by being enclosed in single quotation marks (e.g.,'Hamlin' sweet orange) or preceded by cv (e.g., Citrus sinensis Osbeck cv. Hamlin. Examples of cultivar categories distinguished under the Cultivated Plant Code follow: A clone or several closely similar clones, including distinguishable bud mutations derived from a clone. Note, however, that neither a clone nor any other category listed is designated as a cultivar (variety) until it has been released; i.e., when the name is validly published under prescribed rules. One or more lines of normally self-pollinating individuals or inbred lines of normally cross-pollinating individuals. Cross-pollinated individuals that may show genetic differences but have one or more characters by which they can be differentiated from other cultivars of like or different origin. An assemblage of individuals reconstituted on each occasion by crossing, including single crosses, double crosses, three-way crosses, top crosses, and intervarietal hybrids the primary difficulty in the foregoing categories, which refer to cultivated plants produced principally by systematic breeding and release to growers, is the necessity for continual redefinition of guidelines for classifying populations (i.e. the establishment of precise criteria), particularly those of cultivated plants produced by sexual means such as agricultural agronomic), vegetable, tree, shrub, and flower seeds. General practice for the latter includes the substitution of common for scientific names and variety for cultivar, variety being specifically defined as the International Code of Nomenclature of Cultivated Plants. Cf. Federal Seed Act of 1938 as Amended and Regulations (1976). Guidelines for classifying cultivated plant populations (1978), and Plant patents.

cultivation escape Species may have escaped from gardens, cultivation or both, source not specific but includes some crop and pasture species.

cultriform adj. Curved like a short, wide scimitar; shaped like a knife or plowshare; curved and asymmetric.

cuneate (L. cuneatus: wedge-shaped) adj. Narrowly triangular with the acute angle toward the base; wedge-shaped; tapering toward the point of attachment; in the form of a rounded isoscele triangle with the blunt end outermost; e.g. the wedge-shaped apical cell of hornworts and some thalloid liverworts, the base of the leaves of Vaccinium angustifolium. Cf. tetrahedral, dolabrate. Syn. cuneiform.

cuneifoliate (L. cuneus, cunei; wedge; folium: leaf) adj. With wedge-shaped (cuneate) leaves.

cuneiform (L. cuneus, cunei; wedge; forma: shape) adj. Having the form of a wedge. See cuneate.

Cunninghamian n. A stage in the Devonian of Australia, underlain by the Merionsian, overlain by the Condobolinian, and roughly contemporaneous with the Emsian and Eifelian Stages of Europe.

cunonioid adj. Said a leaf tooth in which the principal vein branches below the tooth, one branch proceeding to the sinus or towards the tooth above, the other proceeding along the upper edge of the tooth to the small glandular apex.

cup n. The cup-like involucre surrounding an acorn.

cupped form Having an open center, with the stamens visible.

cupreous (L. cupreus: of red copper) adj. With coppery appearance,; copper colored.

cupressoid (L. cupressus: cypress; Gr. eid˘: to look like) adj. With foliage like cypress,

cupular See cupulate.

cupulate adj. Cup-shaped, rounded and swollen; e.g. the open capsule of Physcomtrium, Phasconica. Also cupuliform. Cf. cyathiform.

cupule n. A hard or membranous cup-shaped structure formed from bracts and enclosing various fruits, such as the hazelnut and acorn. A structure in club mosses (Lycopodium species) that protects the gemma (resting bud) during its development. It is composed of six leaflike structures. The bright red tissue around the seed of yew (Taxus), forming the yew 'berry'.

cupuliform adj. Nearly hemispherical, cup-shaped. Also cupular. See cupulate.

curcumin A dimer of hydroxycinnamic acid, i.e. with hydroxy (and other) groups attached to the phenolic ring of cinnamic acid, orange-yellow in colour.

curvate adj. Flexing or bending from a straight line.

curved adj. Said of leaf ptyxis, the leaf surface with the margins broadly curved in an adaxial direction, i.e. adaxially concave.

curvinerved adj. Having curved parallel veins, as the leaf of a dogwood.

cushion n. An enlarged area of tissue around the insertion of a petiole into a stalk, or a petiolule into a rachis. Refers to plants which have a rounded shape with low, packed branches, such as cushion Chrysanthemums.

cusp (L. cuspis: point) n. A rigid, sharp point, especially on a leaf.

cuspate See cusped.

cuspated See cusped.

cusped (L. cuspis: point) adj. Having a cusp or cusps; cusplike. Syn. cuspate. cuspated.

cuspidal (L. cuspidare: to make pointed) adj. Of, like, or having a cusp; cuspidate.

cuspidate (L. cuspidare: to make pointed) adj. Tipped with a short, rigid point (cusp); having a cusp or cusps. Syn. cuspidated; e.g. the bud scales of Vaccinium angustifolium. Cf. apiculate.

cuspidated See cuspidate.

cutan n. A complex, insoluble biopolymer with waterproofing qualities found in the cuticle of plants.

cuticle (L. cuticula: diminutive of cutis: skin) n. A continuous impervious layer of fatty substances covering over the outer surfaces of the epidermis of plants; it contains cutin, cutan, or a mixture of both, and protects against water loss and gases. Also cuticula, cuticule.

cuticula See cuticle.

cuticule See cuticle.

cutin (L. cutis: skin) n. A waxy substance (complex biopolymer comprising a mixture of fatty-acid derivatives) with waterproofing qualities which, together with cellulose, forms the outer layer of the skin of many plants, the cuticle.

cutting n. A part, such as a stem, leaf, or root, removed from a plant to propagate a new plant, as through rooting or grafting.

cutting face Applied to the wall surface(s) of the apical cell from which partitioning of derivatives occur; each cutting face becomes the basiscopic surface of a merophyte following separation of the derivative from the apical cell; includes all surfaces or faces except the free surface of the apical cell.

cyanid See cyanide.

cyanide n. Any of various salts or esters of hydrogen cyanide containing a CN group, especially the extremely poisonous compounds potassium cyanide and sodium cyanide. Also cyanid.

cyanidin n. An anthocyanidin.

cyanobacteria n. prokaryotic organisms without organized chloroplasts but having chlorophyll a and oxygen-evolving photosynthesis; capable of fixing nitrogen in heterocysts; occurring in lichens both as primary photobionts and as internal or external cephalodia; still commonly called blue-green algae.

cyanobiont n. The cyanobacterial photosynthetic partner in a lichen symbiosis.

cyanogenesis n. The production of hydrocyanic acid, HCN, by hydrolysation of cyanogenic glycosides.

cyanogenetic See cyanogenic.

cyanogenic adj. Capable of producing cyanide (as hydrogen cyanide). Also cyanogenetic.

cyanophilous adj. Readily absorbing a blue stain such as cotton blue or gentian violet.

Cyanophyta n. A taxonomic division containing cyanophytes, cyanobacteria, and blue-green algae. These may be single cells or colonies, and reproduce by fission. They are found in many environments: damp soil and rocks, fresh water, and salt water.

cyathia See cyathium.

cyathiform (Gr. kyathos: cup; L. forma: shape) adj. With the form of a cyathium; cup-shaped. Cf. cupulate.

cyathium (Gr. kyathos: cup) n. (pl. cyathia) A type of inflorescence characteristic of some members of Euphorbiaceae, e.g. poinsettia; consisting of a cuplike involucre bearing unisexual flowers, staminate on its inner face, pistillate from the base, surrounded by involucral bracts; i.e. consisting of a cup-shaped involucre enclosing an apetalous, pistillate flower surrounded by several staminates flowers.

cyathophorous (Gr. kyathos: cup, phora: carrying) adj. Having a cyathium or cyathia. See cyathium.

cybrid n. The hybrid cytoplasm from protoplast fusion.

cycad (Gr. ko´x, ko´kos: palm tree) n. Any plant of the order Cycadales, consisting of palm-like, cone-bearing, evergreen tropical plants that reproduce by means of spermatozoids and have large pinnately compound, usually fan-shaped, leaves. n. A gymnosperm plant belonging to the phylum Cycadophyta, order Cycadales, (about 100 species), native to warm and tropical regions; the cycad resemble small palms or tree ferns, having short stout stems with a crown of frondlike leaves, usually fan-shaped; reproductive organs are in the form of separate male and female cones borne on different trees, the female cones often being very large (up to 45 kg); the stems of some species yield a type of sago.

Cycadophyta (Gr. ko´x, ko´kos: palm tree: phyton: plant) n. A phylum of seed plants (see gymnosperm) that contains many extinct species; the few modern representatives of the group include Cycas and Zamia. Cycads inhabit tropical and subtropical regions, sometimes growing to a height of 20 m. The stem bears a crown of fernlike leaves. These species are among the most primitive of living seed plants.

cyclic (L. cyclicus: cyclic) adj. Of floral organs, several borne at the same level on the axis; whorled. Cf. spiral.

cyclocytic adj. Said of stomata, with five or more small subsidiary cells surrounding the guard cells.

cyclopentenoid n. A cyanogenic glycoside producing HCN, often found as cyclopentenyl fatty acids.

cygneous adj. Curved suddenly downward, like a swan's neck; e.g. the setae in many species of Campylopodium and Campylopus.

cylindraceous See cylindric.

cylindric adj. Having the shape of a cylinder; rod-shaped; elongate and circular in transverse-section, usually 2-3 times as long as wide. Also cylindraceous, cylindroid, cylindrical.

cylindrical See cylindric.

cylindroid See cylindric.

cyma See cyme.

cymbiform (Gr. kymbŕ: cup, vase, bowl) adj. Boat-shaped and concave; e.g. the leaves of Fontinalis novae-angliae var. cymbifolia.

cyme (Gr. kyma: something swollen) n. A flat-topped or round-topped determinate inflorescence, paniculate, in which the terminal flower blooms first, at the tip of a growing axis and further flowers are formed on branches arising below it, i.e. the outer flowers open last; ex: elderberry (Sambucus).

cymose (Gr. kyma: something swollen) adj. Bearing a cyme or cymes; in the manner of a cyme.

cymose inflorescence A type of flowering shoot (see inflorescence) in which the first-formed flower develops from the growing region at the top of the flower stalk. Thus no new flower buds can be produced at the tip and other flowers are produced from lateral buds beneath. In a monochasial cyme (or monochasium), the development of the flower at the tip is followed by a new flower axis growing from a single lateral bud. Subsequent new flowers may develop from the same side of the lateral shoots, as in the buttercup, or alternately on opposite sides, as in forget-me-not. In a dichasial cyme (or dichasium), the development of the flower at the apex is followed by two new flower axes developing from buds opposite one another, as in plants of the family Caryophyllaceae (such as stitchwort). Cf. racemose inflorescence, cyme.

cymule (Gr. kyma: something swollen) n. A diminutive cyme, usually few-flowered.

cynarrhodia See cynarrhodium.

cynarrhodium (Gr. kynorodon: wild rose) n. (pl. cynarrhodia) A fleshy, hollow fruit enclosing achenes, as the rose hip.

cyphella n. (pl. cyphellae) A break in the lower cortex of a lichen thallus which is rounded or ovate or effigurate and in section appears as an inverted cup-like structure lined with a layer of loosely connected frequently globular cells distinct from the medulla, characteristic of the genus Sticta.

cyphelloid n. A cup-like or tube-like fruiting body with smooth hymenium.

cypsela (Gr. kypselŕ: vase, chest, cup) n. (pl. cypselae) A dry single-seeded indehiscent fruit (that does not split open during seed dispersal) with an adnate calyx and is formed from a double ovary in which only one ovule develops into a seed; it is similar to an achene and is characteristic of members of the family Compositae (Asteraceae), such as the dandelion. Cf. achene. See also pappus.

cypselae See cypsela.

cyst (Gr. kystis: swollen sac, bladder) n. A sporelike cell with a resistant, protective wall; a cell or cavity enclosing reproductive bodies.

cystidia See cystidium.

cystidium (Gr. kystis: swollen sac, bladder) n. (pl. cystidia) In certain basidiomycetous fungi, one of the large, inflated, sterile cells, growing between the basidia and usually projecting beyond them.

cystine n. A white crystalline amino acid, formed from the disulfide linkage of two cysteines during folding of many proteins, especially keratin, and stabilizing the tertiary structure of the protein.

cystisine n. A quinolizidine alkaloid.

cystitis n. Inflammation of the urinary bladder.

cystocarp (Gr. kystis: swollen sac, bladder; karpos: fruit) n. The mass of carpospores formed as a result of fertilization in red algae, with or wihout a special envelope.

cystolith (Gr. kystis: swollen sac, bladder; lithos: stone) n. A mass of calcium carbonate concretion, occasionally silica, formed on ingrowths of modified epidermal cell walls in some plants, especially from the Acanthaceae family.

cytochimera n. A chromosomal chimera; e.g. one having different chromosome numbers in the layers; similar but not necessarily identical to a mixoploid.

cytokinesis n. The division of cytoplasm into cells.

cytokinin n. Any of a group of plant growth substances chemically related to the purine adenine. Cytokinins stimulate cell division in the presence of auxin and have also been found to delay senescence, overcome apical dominance, and promote cell expansion. Zeatin is a naturally occurring cytokinin. Carefully formulated mixtures of cytokinins and auxins are used in micropropagation to generate cloned plantlets from undifferentiated callus tissue.

cytological adj. See cytology.

cytology n. The study of cells.

cytoplasm (Gr. kytos: what covers; plasma: something molded) n. The part of the protoplasm that is not the nucleus. It is a complex, gel-like material containing soluble proteins and small molecules, which is supported by filamentous proteins that constitute the cytoskeleton. Also included are membrane-bound organelles, such as mitochondria, Golgi bodies, and other structures essential to the functioning of the cell.

cytoplasmic adj. Of the cytoplasm.

cytoplasmic inheritance The transmission of hereditary characters through the cytoplasm as distinct from transmission by genes carried by chromosomes; it is detected by differing contribution of male and female parents in reciprocal crosses.

cytoskeleton n. The network of protein filaments and microtubules in the cytoplasm that controls cell shape, maintains intracellular organization and, in some organisms, is involved in cell movement.