habit (L. habitus: external look, condition, appearance, dress) n. The external appearance or way of growth of a plant, e.g. climbing, erect, bushy, etc., comprising its size, shape, texture and orientation; the tendency of a plant to grow in a certain way. A plant's habit may be described as creeping, trees, shrubs, vines, etc.

habitat (L. habitare: to inhabit) n. The locality or external environment in which a plant lives. The natural dwelling place of an animal or plant; the type of environment where a particular species is likely to be found,

hadrom See hadrome.

hadrome n. The tracheary elements and associated parenchymatic cells of xylem tissue. Also hadrom.

haemochorin n. An arylphenalenone.

hair n. An epidermal outgrowth composed of a single elongated cell. In lichens, a multicellular outgrowth from the cortex. See awn, arista.

hairy adj. Pubescent with longer hairs.

halberd-shaped See hastate.

half-inferior adj. Attached below the lower half, as a flower with a hypanthium that is fused to the lower half of the ovary, giving the appearance that the other floral whorls are arising from about the middle of the ovary. Of an ovary, partly below and partly above the level of attachment of the perianth and stamens.

halonate adj. Said of the outer layer of spores, surrounded by a transparent coat.

halophile (Gr. als, alos: salt; philos: friend, loved) n. A halophilous plant (or animal).

halophilous (Gr. als, alos: salt; philos: friend, loved) adj. Of a plant (or animal) thriving in a saline environment.

halophyte (Gr. als, alos: salt; phyton: plant) n. A plant that can tolerate a high concentration of salt in the soil. Such conditions occur in salt marshes and mudflats. Halophytes possess some of the structural modifications of xerophytes; for example, many of them are succulents. In addition, they are physiologically adapted to withstand the high salinity of the soil water: their root cells have a higher than normal concentration of solutes, which enables them to take up water by osmosis from the surrounding soil. Examples of halophytes are mangrove trees (see mangrove swamp), thrift (Armeria), sea lavender (Limonium), and rice grass (Spartina). Cf. hydrophyte; mesophyte.

halophytic adj. See halophyte.

halotolerant adj. Tolerant of higher salt concentrations.

hamate (L. hamatus: hooked) adj. Hook-shaped; hooked at the tip; more abruptly curved than falcate. Syn. hamose, hamous.

hamathecia See hamathecium.

hamathecium n. (pl. hamathecia) A neutral term for all kinds of hyphae or other tissues between asci, or projecting into the locule or ostiole of an ascoma.

hamaudol n. A pyranochromone.

hamose (L. hamus: hook) adj. See hamate.

hammock n. See hummock.

hamous (L. hamus: hook) adj. See hamate.

hapaxanthic (Gr. apax: only once; anthos: flower) adj. Flowering only once.

haplocaulis (Gr. apls: plainly, simply; kaulos: stem) adj. With an unbranched stem.

haplocheilic adj. Meaning perigenous when about the gymnosperm stomatal ontogeny.

haplochlamydeous (Gr. apls: plainly, simply; khlamis: cloak, mantle) adj. See monochlamydeous.

haploid (Gr. apls: plainly, simply; eidos: form) adj. Describing a nucleus, cell, or organism with a single set of unpaired chromosomes, i.e. having each gene locus represented only once, i.e. where the diploid number of chromosomes reduced by half; the haploid number is designated as n. This occurs in higher organisms when gametes, reproductive cells, are formed as a result of meiosis; gametes are then haploid. Fusion of two such cells, fertilization, restores the normal,diploid number.

haplolepideous See haplolepidous.

haplolepidous adj. Form of arthrodontous peristome; originally: having main teeth formed from a single column of cells up dorsal face; strictly: having only one circle of teeth derived from thickening of the contiguous walls of the primary and inner peristomial layers (homologous to the inner diplolepidous circle, endostome). Cf. diplolepidous, sesquilepidous. Also haplolepideous.

haplomorphic adj. Said of a flower with no obvious plane of symmetry, yet not obviously asymmetrical either, any two halves being very similar, e.g. Magnolia.

haplopetalous (Gr. apls: plainly, simply; petalon: leaf) adj. With a single series of petals

haplophase n. The part of the life cycle where the cells are haploid.

haplophyte (Gr. apls: plainly, simply; phyton: plant) n. Having the number of chromosomes characteristic of the gametes for the organism.

haplostele (Gr. apls: plainly, simply; stl: stele) n. An haplostele is the simplest protostele; it consists of a solid core of xylem surrounded by a layer of phloem; an endodermis surrounds the stele. See stele, protostele.

haplostemonous (Gr. apls: plainly, simply; stmn: thread) adj. With one series of stamens; with as many stamens as petals

hapteron (Gr. apt: to tie, fasten) n. (pl. haptera) Holdfast, specialized root-like projections that function to anchor a plant. An aerial organ of attachment of some fruticose lichens (Alectoria, Bryoria, Usnea) formed by a secondary branch which becomes attached to the substratum.

haptotropic (Gr. aptikos: specific to the touch; tropos: direction) adj. See haptotropism.

haptotropism n. An orientation response of an organism to stimulation by touch. Cf. thigmotropism.

hard frost A frost where both the air and the soil has dropped below freezing. Many plants can survive a light frost but cannot survive a hard frost.

hardiness n. The ability of a plant to withstand winter cold and summer heat.

hardpan n. A layer of soil sufficiently clogged with clay or other particles which often prevents the penetration of water and shrub or tree roots; hard, unbroken ground.

hardwood adj.; n. Made of hard-to-cut wood of a broad-leaved tree, e.g. oak; the wood of a broad-leaved dicotyledonous tree, as distinguished form the wood of conifers. A dicotyledonous tree.

hardy adj. A term used regarding plants that describes their ability to withstand the cold of winter in the open air. It does not mean that the plant is long-living, pest resistant, or drought tolerant.

hastate (L. hastatus: armed with a spear) adj. Spear shaped, more or less triangular with the two basal lobes divergent, pointing outwards, spreading approximately at right angles; abruptly broadened and auriculate at base. Syn. halberd-shaped, hastiform.

hastiform (L. hasta: spear, pike; forma: shape) adj. See hastate.

haustauria See haustorium. Also haustoria.

haustaurium n. (pl. haustauria) See haustorium.

haustoria See haustorium.

haustorium (L. haustor, haustoris: one who draws, one who drinks) n. (pl. haustauria) A specialized structure of certain parasitic plants and fungi that penetrates the cells of the host plant to absorb nutrients. In parasitic fungi haustoria are formed from enlarged hyphae and in parasitic flowering plants, such as the dodder (Cuscuta), they are outgrowths of the stem. In bryophytes, an elongate cell(s) at the base of the foot, most prominent in the embryonic sporophyte; thought to function in absorption during early stages of sporophyte growth. In lichens, a special hyphal branch, especially one within a living cell of the host, for absorption of nutrients Also haustaurium.

head n. A dense cluster of sessile or nearly sessile flowers on a very short axis or receptacle; the involucrate inflorescence of the Compositae (Asteraceae)

heartwood n. See duramen.

heath n. An extensive area of rather open uncultivated land usually with poor coarse soil and covered with low shrubs; any plant of the genus Erica or of the family Ericaceae.

heathland n. A tract of level wasteland; uncultivated land with sandy soil and scrubby vegetation. See also heath.

heave v. Alternate freezing and thawing of soil causing a plant to be pushed upward and often exposing its roots to damage.

heaving n. See heave.

hebecarpous (Gr. be: puberty; karpos: fruit) adj. With pubescent fruit.

hebecladous (Gr. be: puberty; klados: branchlet, branch) adj. With pubescent branches.

hebegynous (Gr. be: puberty; gyn: female) adj. With pubescent pistils.

hebepetalous (Gr. be: puberty; petalon: leaf) adj. With pubescent petals

hebetate (L. hebes: dull) adj. v. With a soft, blunt termination. To make dull.

hebete (L. hebes: dull) adj. Dull.

helical adj. Coiled or spiraled; spirally twisted; said of a spiral segmentation sequence from the apical cell. Cf. pendular. Also helicoid.

helicoid (Gr. elix, elikos: spiral; eid: to look like) adj. Coiled like a spiral or helix; of a cymose inflorescence, branching repeatedly on the same side.

heliophilous (Gr. lios: sun; philos: friend) adj. Growing in sunny places; adapted to, or capable of, growing in full sunlight.

heliophyte adj., n. (Of) a plant that grows in full sunlight.

heliotaxis (Gr. lios: sun; taxis: arrangement) n. Movement of an organism toward or away from sunlight.

heliotrope (Gr. lios: sun; tropos: direction) n. Any plant that turns towards the sun.

heliotropic (Gr. lios: sun; tropos: direction) adj. Turning or growing toward the light.

heliotropism n. Growth or orientation of an organism, especially a plant, toward or away from the light of the sun.

helobial adj. Said of endosperm formation, when the endosperm immediately divides into two cells of unequal size, a larger micropylar and a smaller chalazal, and in the micropylar chamber at least subsequent nuclear division is not accompanied by wall formation.

helohylophilous adj. Thriving in wet forests.

helophyte n. A cryptophyte that mainly grows in soil saturated with water or in the water itself, and from which leaf and flower-bearing shoots emerge. Helophytes do not include all the plants ordinarily known as marsh plants. adj. Said of life forms, for plants with resting buds at the bottom of the water, but with emergent axes, a cryptophyte. Also helophytic.

helophytic adj. See helophyte.

hemagglutinin n. An antibody that agglutinates erythrocytes, commonly found in plant seeds.

hemi- (Gr. mi: half) prefix. Meaning half.

hemianatropous See hemitropous.

hemianatropous ovule See hemitropous ovule.

hemiangiocarpic adj. Said of a sporocarp, opening before quite mature.

Hemiascomycetae n. A class of the phylum Ascomycota. It is morphologically simple, with a short mycelia or none at all. Also Hemiascomycetes.

Hemiascomycetes See Hemiascomycetae.

hemiascomycetous adj. Of fungi which belong to the class of the Hemiascomycetes.

hemicarp See mericarp.

hemicellulose n. A matrix of polysaccharides containing galactose, xylose, etc., and cross-linking cellulose molecules.

hemicryptophyte (Gr. mi: half; kryptos, hidden; phyton, plant) n. Perennial (or biennial) herbaceous plant in which the stems die back to a remnant shoot system that lies on the ground. These are herbaceous plants with runners along the ground; its overwintering buds located at the soil surface.

hemidiscoid adj. Like a half-disc; applied to a prismatic apical cell with three segmenting surfaces. Cf. prismatic.

hemiepiphyte See hemi-epiphyte.

hemi-epiphyte (Gr. mi: half; epi: upon, above; phyton: plant) n. A plant that germinates on other plants and then establishes soil contact; or a plant that germinates on the ground but later loses contact with the soil. Hemi-epiphytes use other plants for support, at least during part of their life. The strangler fig is an interesting hemi-epiphyte: it starts life as an epiphyte, growing on other trees; as it matures it sends down roots to the ground, and slowly, over many years, the fig encloses and strangles the tree that was its nursery.

hemiepiphytic adj. Remaining rooted in the ground but climbing tree trunks. Cf. hemiepiphyte.

hemi-epiphytic See hemiepiphytic.

hemiparasite (Gr. mi: half; parasitos: parasite) n. A parasitic plant that lacks a fully developed root system and forms connections with another plant, from which it obtains some or all of its water and minerals. Such plants have chlorophyll and produce their own food by photosynthesis, and in some cases are capable of limited growth in the absence of the host plant. They tap into the sap-conducting tissue of the host by means of specialized structures called haustoria (see haustorium). Some, such as eyebright (Euphrasia spp.), attach themselves to the roots of their host and appear like normal plants growing in the soil, whereas others grow on the aerial parts of their host. The mistletoes are well-known examples that colonize the branches of trees. . A facultative parasite (see parasitism).

hemispheric (Gr. mi: half; sphaira: sphere) adj. Shaped like half of a sphere.

hemispherical See hemispheric.

hemispheroidal (Gr. mi: half; sphaira: sphere; eid: to look like) adj. Shaped like half of a spheroid.

hemitropous adj. Said of an ovule, half inverted, the micropyle being at right angles to the funicle and the body of the ovule straight.

hemitropous ovule An ovule which is half inverted so that the funiculus is attached near the middle with the micropyle at right angle

hemoglobin n. A protein complex found in the blood of most chordates and the roots of certain legumes. It binds oxgen molecules, and in chordates serves as the means by which the oxygen is supplied to the cells of the body.

hemostatic (Gr. aima: blood; statikos: specific to stopping) adj., n. Arresting hemoraghe, as a drug; a hemostatic agent or substance.

hemp n. The course fibers used to make cordage derived from plants of the genus Cannabis, or other similar plants. A plant of the genus Cannabis.

hepatic adj. Acting on the liver, as a medicine.

hepaticous (Gr. par, patos: liver) adj. Liver-colored.

Hepatophyta (Gr. par, patos: liver; phyton: plant) n. A phylum comprising the liverworts - simple plants that lack vascular tissue and possess rudimentary rootlike organs (rhizoids). Liverworts occur in moist situations (including fresh water) and as epiphytes on other plants. Like the mosses (see Bryophyta), liverworts show marked alternation of generations between haploid gamete-bearing forms (gametophytes) and diploid spore-bearing forms (sporophytes), the latter being dependent on the former for nutrients, etc. The plant body (gametophyte) may be a thallus, growing closely pressed to the ground (thallose liverworts, e.g. Pellia), or it may bear many leaflike lobes (leafy liverworts). It gives rise to leafless stalks bearing capsules (sporophytes). Spores formed in the capsules are released and grow to produce new plants. Liverworts were formerly placed in the class Hepaticae, in the phylum Bryophyta, which now contains only the mosses.

heptamerous (Gr. epta: sevwen; meros: part) adj. With parts in sevens; of flowers having seven membres in each whorl..

herb (L. herba: plant, herb) n. Generally any plant which does not produce wood, and is therefore not as large as a tree or shrub, is considered to be an herb; any seed plant whose stem withers away to the ground after each season's growth; a seed plant with a green, non-woody stem. There are several types of herbs, including: forbs, i.e. broad-leaved herbs, graminoids, i.e. grass-like herbs, with very narrow leaves, ferns, i.e. herbs with broad but highly dissected leaves and no flowers, herbaceous vines, i.e. non-woody plants that climb on other plants. Cf. forb.

herbaceous (L. herba: plant, herb) adj. Not woody; soft in texture. Having little or no woody tissue; leaf-like in color and texture. Said of a plant which dies back to the roots each year during winter, as opposed to a plant which remains green all winter.

herbaceous vines Non-woody plants that climb on other plants.

herbage (L. herba: plant, herb) n. Herbs collectively; the green foliage and juicy stems of herbs; the non-reproductive parts of the plant; the non-woody stems, leaves, and roots of a plant.

herbal adj., n. A book about herbs, usually illustrated. Of, or relating to, herbs.

herbalism n. The cultivation, collection, study and use of herbs, particularly for medicinal purposes.

herbalist n. One who practices herbalism.

herbaria See herbarium.

herbarium (L. herbarium: work on botany) n. (pl. herbaria) An organized and cataloged collection of plant specimens. A place housing such a collection.

heritability The proportion of variability that results from genetic causes; equivalent to total genetic variation, which is total variation less environmental variation; also that proportion of the variation of a population that is transmitted to progeny.

herkogamous adj. See herkogamy.

herkogamy n. Where pollen presentation and pollen receipt is spatially separated within an individual flower, or between individual plants, so ranging from cases where the stamens and stigma are in different places in the same flower to dioecy, where stamens and stigmas are on diffferent plants. A strategy employed by hermaphroditic angiosperms to reduce sexual interference between male (anthers) and female (stigma) function by suplying a spatial separation of the anthers and stigma.

hermaphrodite (Gr. Ermaphroditos: son of Hermes and Aphrodite, then: hermaphrodite) n. A hermaphroditic plant.
adj. Qualifies a plant or animal that has both male and female reproductive organs and secondary sexual characteristics. Also hermaphroditic.

hermaphroditic (Gr. Ermaphroditos: son of Hermes and Aphrodite, then: hermaphrodite) adj. With pistils and stamens in the same flower; bisexual; monoclinous; perfect.

hermaphroditism n. When the reproductive organs of both sexes are present in the same individual or in the same flower in higher plants.

heroin n. A narcotic compound that is a synthetic derivative of morphine (see opiate). The compound is easily absorbed by the brain, due to its lipid-like nature, and is used as a sedative and powerful analgesic. Highly addictive, it is abused by drug users. Syn. diacetylmorphine.

herpes n. Any of several viral diseases causing the eruption of small blisterlike vesicles on the skin or mucous membranes, especially herpes simplex or herpes zoster.

Hervyan n. The uppermost stage in the Devonian of Australia, underlain by the Condobolinian Stage, overlain by the Carboniferous, and roughly contemporaneous with the upper Frasnian and Famennian of Europe.

hesperetin n. A flavanone.

hesperidia See hesperidium.

hesperidium (Gr. Esperis, Esperidos: Hesperides) n. (pl. hesperidia) A fleshy berrylike fruit with with sectioned pulp inside a tough separable rind, as a lemon or orange.

heterandrous (Gr. eteros: other; anr, andros: male) adj. With stamens or anthers of different forms or sizes.

hetero- (Gr. eteros: other) prefix. Meaning different or other.

heteroblastic (Gr. eteros: other; blast, blasts: bud, sprout) adj. Having the adult parts of the plant (especially the leaves) distinctly different in form from the juvenile parts.

heterocarpous (Gr. eteros: other; karpos: fruit) adj. With fruit of different kinds.

heterocaryosis n. The presence of two or more genetically different nuclei within single cells of a mycelium.

heterocellular adj. Said when an individual xylem ray has cells of two (or more) kinds.

heterocephalous (Gr. eteros: other; kephal: head) adj. With staminate and pistillate flowers in separate heads, as in some Compositae (Asteraceae).

heterochlamydeous (Gr. eteros: other; khlamis: cloak, mantle) adj. With a perianth composed of distinctly different calyx and corolla whorls.

heterochrony n. An evolutionary change in phenotype based on an alteration in timing of developmental events.

heteroecious (Gr. eteros: other; oikos: house) adj. Spending different stages of a life cycle on different, usually unrelated hosts; used of parasites such as rust fungi and tapeworms; parasitic on alternating hosts; starting life on one organism, then affecting a second species.

heterogameon n. A species made up of races that if selfed, produce morphologically stable populations; apomixis is not present.

heterogamete (Gr. eteros: other; gamet: spouse) n. Either of two conjugating gametes that differ in structure or behavior, such as the small motile male spermatozoon and the larger nonmotile female ovum. Also anisogamete.

heterogamous (Gr. eteros: other; gamos: marriage) adj. With flowers of differing sex; producing flowers of two or more kinds with respect to their fertile organs, e.g. male and female or bisexual and female; rregular as regards stamens and pistils. Cf. homogamous.

heterogamy (Gr. eteros: other; gamos: marriage) n. Having heterogamous flowers, a state in which the flowers of a plant are of two types.

heterogeneous (Gr. eteros: other; genea: what is generated) adj. Composed of dissimilar parts. Cf. homogeneous.

heterogenesis n. The alternation of generations, especially a unisexual dioecious alternating with one or more parthenogenetic generations.

heterogonous (Gr. eteros: other; gonos: generation) adj. With two or more different kinds of perfect flowers on different individuals of the same species, the kinds of flowers differing in the relative length of the pistils and stamens; irregular as regards stamens and pistils. Cf. homogonous.

heterogony (Gr. eteros: other; gonos: generation) n. The state of being heterogonous. The alternation of generations, especially of a sexual and hermaphroditic generation.

heteroicous adj. With several forms of gametoecia on the same plant (or various plants of the same species). Also polyoicous, polygamous, heteroecious. Cf. autoicous.

heteromallous adj. Pointing in all directions; turned in different directions. Cf. homomallous.

heteromerous (Gr. eteros: other; meros: part) adj. With a variable number of parts, as in a flower with a different number of members in each floral whorl; not isomerous; in lichens : having mycobiont and photobiont components in well-defined layers, with the photobiont in a more or less distinct zone between the upper cortex and the medulla.

heteromorphic (Gr. eteros: other; morph: shape) See heteromorphous.

heteromorphous (Gr. eteros: other; morph: shape) adj. Of two or more distinct forms; of more than one kind or form. Syn. heteromorphic.

heterophyllous (Gr. eteros: other; phyllon, leaf) adj. The presence on a single individual of two or more distinct leaf shapes; these leaves may differ markedly in shape, yet have similar gross anatomical organization; e.g. Racopilium.

heterosis n. Hybrid vigor such that an F1 hybrid falls outside the range of the parents with respect to some character or characters. Usually applied to size, rate of growth, or general thriftiness.

heterosporangiate (Gr. eteros: other; spora: seed; aggeion; bowl, container) adj. Producing two different kinds of sporangia, specifically microsporangia and megasporangia. Cf. heterosporous.

heterosporous (Gr. eteros: other; spora: seed) adj. Producing two different sizes or kinds of spores. These may come from the same or different sporangia, and may produce similar or different gametophytes. Producing separate male and female spores. Cf. homosporous, anisosporous, heterosporangiate.

heterospory (Gr. eteros: other; spora: seed) n. The condition of producing two types of spore, megaspores and microspores. Heterospory occurs in all seed-bearing plants and in some mosses and ferns.

heterostyled (Gr. eteros: other; stylos: column, pilar) adj. Of a plant having styles of different forms or lengths in the flowers. Also heterostylous. Cf. homostylous.

heterostylic See heterostylous.

heterostylous (Gr. eteros: other; stylos: column, pilar) adj. Said of species in which flowers are similar except that the stigmas and anthers are held at different levels relative to each other, because style length differs between plants. Cf. homostylous. Also heterostylic, heterostyled. Cf. homostylous.

heterostyly (Gr. eteros: other; stylos: column, pilar) n. See heterostylous.

heterothallic (Gr. eteros: other; thallos: young shoot) adj. Having mycelia of two unlike types both of which must participate in the sexual process. Cf. homothallic.

heterothallism n. The condition of sexual reproduction in which conjugation is possible only through the interaction of different mating types.

heterothally n. The haploid incompatibility in fungi (opposite of homothally).

heterotroph See heterotrophic.

heterotrophe n. See heterotrophic. Also heterotroph.

heterotrophic (Gr. eteros: other; troph: food) adj. Capable of utilizing only organic materials as a source of food, as most animals and some plants. Also heterotrophe, heterotroph.

heterotrophically (Gr. eteros: other; troph: food) adv. See heterotrophic.

heterotrophic nutrition (Gr. eteros: other) A type of nutrition in which energy is derived from the intake and digestion of organic substances, normally plant or animal tissues. The breakdown products of digestion are used to synthesize the organic materials required by the organism. All animals obtain their food this way: they are heterotrophs. Cf. autotrophic nutrition.

heterotrophy (Gr. eteros: other; troph: food) n. The ability or requirement to synthethise all metabolites from organic compounds. See heterotrophic.

heterotypic division See reductive division.

heterozygote (Gr. eteros: other; zygos: yoke) n. An organism or cell having two different alleles of a particular gene or genes at corresponding loci on homologous chromosomes, and so giving rise to varying offspring. Cf. homozygote.

heterozygous (Gr. eteros: other; zygos: yoke) adj. Describing an organism or cell in which the alleles at a given locus on homologous chromosomes are different. The aspect of the feature displayed by the organism will be that determined by the dominant allele. Heterozygous organisms, called heterozygotes, do not breed true. Cf. homozygous.

hexa- (Gr. ex, six) prefix. Meaning six.

hexagynous (Gr. ex: six; gyn: female) adj. With six pistils.

hexamerous (Gr. ex, six; meros: part) adj. With parts arranged in sets or multiples of six.

hexandrous (Gr. ex, six; anr, andros: male) adj. With six stamens.

hexapetalous (Gr. ex, six; petalon: leaf) adj. With six petals.

hexaphyllous (Gr. ex, six; phullon, leaf) adj. With six leaves

hexaploid (Gr. ex, six; eidos: form) n. Having six full sets of chromosomes in each cell.

hexitol n. A sugar alcohol with six -OH groups.

hexose n. A six-carbon sugar, e.g. fructose, sucrose.

hibernacle See hibernaculum.

hibernacula See hibernaculum.

hibernaculum (L. hibernacula, winter baracks) n. (pl. hibernacula, hibernaculas) A plant organ such as a bud, rhizome, turion, etc., which allows a plant to live through adverse conditions; the protective covering of an animal or a plant that protects it during its dormant stage in the winter. The winter quarters of a hibernating animal. Also hibernacle.

hibernal (L. hibernalis: of winter) adj. Flowering or appearing in the winter.

hilum (L. hilum: a little thing, a trifle) n. A scar on the seed coat of a plant marking the point at which the seed was attached to the fruit wall by the funicle during development. It is a feature that distinguishes seeds from fruits.

hip n. A berry-like structure composed of an enlarged hypanthium surrounding numerous achenes, as in roses, i.e. the closed and ripened receptacle of a rose which contains the seed.

hippocrepiform (Gr. ippos: horse; L. crepis: shoe; forma: shape) adj. Horseshoe-shaped.

hirsute (L. hirsutus: bristly) adj. Set with bristles; hairy; shaggy; bearing coarse, rough, longish hairs. Cf. villous.

hirsutulous diminutive of (L. hirsutus: bristly) adj. Pubescent with very small, coarse, stiff hairs.

hirtellate See hirsutulous.

hirtellous See hirsutulous.

hispid (L. hispidus: rough, shaggy) adj. Having stiff hairs, spines, or bristles; rough with bristles; bristly; shaggy.

hispidulous (diminutive of L. hispidus: rough, shaggy) adj. Minutely hispid.

histamine A hormone/chemical transmitter (biogenic monoamine, similar to serotonine, epinephrine, norepinephrine) involved in local immune responses, regulating stomach acid production and in allergic reactions as a mediator of Immediate Hypersensitivity. When released from mast cells, histamine causes vasodilation and an increase in permeability of blood vessel walls. These effects, in turn cause the familiar symptoms of allergy including a runny nose and watering eyes. When released in the lungs, histamine causes the airways to swell shut in an attempt to close the door on offending allergens and keep them out. Unfortunately, the ultimate result of this response is the wheezing and difficulty in breathing seen in people with asthma, an occasionally deadly allergic complication which kills an estimated 4000 Americans yearly. Cf. antihistamine.

histogen (Gr. istos: tissue; genna: to produce) n. A region in a plant in which tissues differentiate.

histone See histones.

histones n. Proteins rich in arginine and lysine, soluble in water but not dilute ammonia, attached to the DNA of eukaryotes which allows it to be packaged into chromosomes; i.e. histones occur mainly in the cell nucleus and are concerned with the regulation of DNA.

hives n. Any of various eruptive conditions of the skin, as the wheals of urticaria.

hoary adj. Covered with a greyish layer of very short, closely interwoven hairs.

holarctic adj. Of, relating to, or being the biogeographic region including the northern parts of the Old and the New Worlds and comprising the nearctic and palearctic regions or subregions.

holdfast n. Any of several roolike or suckerlike organs or parts serving for attachment; anchoring base of an alga or lichen, often disc-like.

holobasidia holobasidium.

holobasidium n. (pl. holobasidia) A basidium which is not divided by primary septa.

holocarpic (Gr. olos: whole, entire; karpos: fruit) adj. Of a fungus having the entire thallus converted into fructifications. Syn. holocarpous. See eucarpic.

holocarpous See holocarpic.

Holocene n. The geological period that extends from the end of the Pleistocene period, some 12,000 years ago, up to the present day.

holocoenotic (Gr. olos: whole, entire; koinos: common) adj. Denotes the interdependent parts of a coherent indivisible whole and applies to the interrelationship of nature and humankind; about the theory that environmental factors act as a whole or aggregate in their effect upon organisms.

holometabolism n. The complete form of metamorphosis in which an insect passes through four separate stages of growth, as embryo, larva, pupa, and imago. Also called 'complete metamorphosis'.

holometabolic adj. See holometabolous.

holometabolous adj. Said of certain insects, as the butterflies and bees, undergoing complete metamorphosis. Also said holometabolic.

holophyte n. An organism that produces its own food through photosynthesis.

holophytic (Gr. olos: whole, entire; troph: food) adj. Of a plant obtaining food by synthesising inorganic substances; autotrophic.

holosericeous (Gr. olos: whole, entire; srikos: of silk) adj. Covered with fine, silky hairs.

holotype (Gr. olos: whole, entire; typos: mark, image) n. A single specimen designated by the author of a plant (or animal) name, at the time of original publication, as that to which the name shall apply; the 'voucher specimen' of a name; the holotype serve as the basis for naming and describing a new species or variety. Cf. lectotype, neotype, paratype, syntype, isotype, topotype, cotype, generitype.

homeopath n. One who practises homeopathy. Also homeopathist.

homeopathic adj. See homeopathy.

homeopathically adv. See homeopathy.

homeopathist n. See homeopath.

homeopathy n. A system for treating disease based on the administration of minute doses of a drug that in massive amounts produces symptoms in healthy individuals similar to those of the disease itself.

homo- (Gr. omos: same) prefix. Meaning the same.

homocellular adj. Said when an individual xylem ray has cells of only a single kind.

homochlamydeous (Gr. omos: same; khlamis: cloak, mantle) adj. Referring to a flower in which sepals and petals are so similar that all are called tepals.

homochromous (Gr. omos: same; khrma: color) adj. Being all of one color, as the flower heads of some Compositae (Asteraceae)

homoeandrous (Gr. omos: same; anr, andros: male) adj. With uniform stamens

homoerythrina n. A group of alkaloids derived from tyrosine and phenylalanine.

homogamous (Gr. omos: same; gamos: marriage) adj. Said of a plant with flowers hermaphrodite or of the same sex; with the pistils and stamens maturing at the same time. Having flowers of only one kind. Cf. heterogamous, dichogamous.

homogamy (Gr. omos: same; gamos: marriage) n. The condition in a flower in which the male and female reproductive organs mature at the same time, thereby allowing self-fertilization. Cf. dichogamy.

homogeneon n. A genetically and morphologically homogeneous species in which apomixis is not present and all members are interfertile.

homogeneous (Gr. omos: same; genea: kind) adj. With parts all of the same kind; uniform.

homogonous (Gr. omos: same; gonos: generation) adj. With perfect flowers which do not differ in the relative length of the pistils and stamens. Cf. heterogonous.

homogony (Gr. omos: same; gonos: generation) n. State of being homogonous

homoiomerou adj. Said of lichens having mycobiont and photobiont components intermixed throughout thallus, not layered.

homologous (Gr. omos: same; logos: word, reason) adj. Describing structures in organisms that have a common ancestral origin. Thus the legs of quadruped land animals and the flippers of seals are homologous since the internal arrangements of the bones of each are derived from the same general pattern.

homologous chromosomes Chromosomes having the same structural features. In diploid nuclei, pairs of homologous chromosomes can be identified at the start of meiosis. One member of each pair comes from the female parent and the other from the male. Homologous chromosomes have the same pattern of genes along the chromosome but the nature of the genes may differ. (see allele).

homology (Gr. omos: same; logos: word, reason) n. Two structures are considered homologous when they are inherited from a common ancestor which possessed the structure. This may be difficult to determine when the structure has been modified through descent.

homology of chromosomes Applied to whole chromosomes or parts of chromosome which synapse or pair in meiotic prophase.

homomallous adj. Pointing the same way. Cf. heteromallous.

homomorphic (Gr. omos: same; morph: shape) adj. All of the same kind or form.

homomorphism (Gr. omos: same; morph: shape) n. The possession of perfect floers of only one kind.

homomorphous See homomorphic.

homonym n. A scientific name given two or more times to plants of the same taxonomic rank but which are quite distinct from each other. Cf. basionym, synonym, tautonym, autonym.

homophyllous (Gr. omos: same; phyllon, leaf) adj. Producing the same form of leaf in the winter and summer months.

homoplasy n. Same as convergence.

homosporous (Gr. omos: same; spora: seed) adj. Producing only one kind of spore in the sexual reproductive cycle, and hence one gametophyte which produces both male and female gametes. Having spores of a single appearance and behavior. Cf. heterosporous.

homospory (Gr. omos: same; spora: seed) n.The production of only one kind of spore, neither microspore nor megaspore.

homostyle See homostylous.

homostyled See homostylous.

homostylic See homostylous.

homostylism n. See homostylous.

homostylous (Gr. omos: same; stylos: colonne) adj. With styles of more or less constant length in flowers of the same species; of species in which the flowers have stigmas and anthers held at the same level relative to each other on all plants. Cf. heterostylous. Syn. homostyled, homostylic. Cf. heterostylous. Also homostyle.

homostyly n. See homostylous.

homothallic (Gr. mos: same; thallos: young shoot) adj. Having all mycelia alike, the opposite sexual functions being performed by different cells of a single mycelium. Cf. heterothallic.

homothallism n. A condition where sexual reproduction occurs without the interaction of two different mating types.

homotypic division Cf. reductive division, fruit setting, apomixis.

homozygote (Gr. omos: same; zygos: yoke) n. An individual having two identical alleles of a particular gene or genes, and so breeding true for the corresponding characteristics. Cf. heterozygote.

homozygous (Gr. omos: same; zygos: yoke) adj. Describing an organism or cell in which the alleles at a given locus on homologous chromosomes are identical (they may be either dominant or recessive). Homozygous organisms, which are called homozygotes, breed true when crossed with genetically identical organisms. Cf. heterozygous.

hooded adj. Cucullate.

hooked adj. Abruptly curved at the tip.

Hopkins' law See bioclimatic law.

hormone (orma: to put in motion) n. A chemical produced by organisms to trigger or regulate certain processes.

hornwort n. A plant of the widely distributed genus Ceratophyllum (3 species), which grows submerged in ponds and streams. C. demersum is rootless, with a stem 20 to 100 cm long and simple forked leaves, 1 to 2 cm long. The small flowers produce a three-spined nutlike fruit. Family: Ceratophyllaceae. A nonvascular plant of the phylum Anthocerophyta (or class Anthocerotae; about 100 species), formerly classified as a liverwort; distributed worldwide, hornworts consist of a flat leaflike gamete-producing plant from which arises a long-lived spikelike spore-producing structure, 2 to 5 cm long. See also bryophytes.

horotelic (Gr. ra: at the convenient time; telikos: tending to a definite end) adj. Of or pertaining to evolution at a rate standard for a given group of plants or animals. Cf. bradytelic, tachytelic.

horotely n. See horotelic.

horticulture n. The science or art of cultivating fruits, vegetables, flowers, or ornamental plants. The cultivation of a garden.

horticultural adj. See horticulture.

horticulturally adj. See horticulture.

horticulturist adj., b. See horticulture.

host (L. hospes, hospitis: host) n. An organism whose body provides nourishment and shelter for a parasite (see parasitism) or a parasitoid. A definitive (or primary) host is one in which an animal parasite becomes sexually mature; an intermediate (or secondary) host is one in which the parasite passes the larval or asexual stages of its life cycle; applied, loosely, to a plant supporting an epiphyte).

humate n. Humic acid in its solid state.

humectant adj., n. Producing moisture; a substance added to another substance to keep it moist.

humic adj. Of, relating to, or derived from humus example: humic acids.

humicolous adj. Growing on ground with decomposing organic matter.

humifuse (L. humus; ground; fusus: spreading) adj. Spread over the surface of the ground; procumbent.

humistrate (L. humus; ground; startus: spread, laying flat) adj. Trailing or lying flat, not rooting at the nodes.

hummock n. A low mound or ridge of earth; a knoll. A tract of forested land that rises above an adjacent marsh in the southern United States (also hammock). A ridge or hill of ice in an ice field.

humus (L. humus; ground) n. Decomposing organic material.

husk n. A tough outer covering on some fruits and seeds.

hyalescent (Gr. hyaleos: transparent) adj. Becoming translucent; somewhat hyaline.

hyaline (Gr. hyaleos: transparent) adj. Of thin, membranous, colorless, transparent or translucent texture; almost like clear glass.

hyalocyst n. Large, empty, water-storage cell as in leaves of Sphagnum and Leucobryum, and in many endohyalocysts. Cf. chlorocyst.

hyalocyte n. A cell that differentiates into a hyalocyst.

hyalodermis n. (pl. hyalodermides, hyaloderms) Differentiated external cells; e.g. thickwalled, enlarged or hyaline cells; stem epidermis of enlarged, hyaline cells, i.e. the chloroplasts are very few or lacking; such cells may be protoplasmic (e.g. Cephalozia) or not (e.g. Sphagnum) at maturity

hybrid (L. hybrida: hybrid) n. Any cross-bred plant; heterozygote. An offspring of genetically different parents (in a Flora, usually applied where the parents are of different species). An offspring of two animals or plants of different races, breeds, varieties, species, or genera. The hybrid offspring often shows greater general fitness than either of the two parents, a phenomenon called hybrid vigour (or heterosis). This is commonly used by plant breeders to produce a generation of crop plants giving higher yields and showing improved resistance to disease. Hybrid vigour cannot be maintained in subsequent generations and new hybrids have to be produced for each season.

hybridise v. See hybridize.

hybridisation n. The act of mixing different species or varieties of animals or plants and thus to produce hybrids. Hybridisation is used extensively in agriculture, where new forms of hardy and disease-resistant plants are produced commercially. Also hybridization.

hybridization n. See hybridisation.

hybridize (L. hybrida: hybrid) v. Crossbreeding two species to create a plant with some characterisitics of each parent. Also hybridise.

hybrid swarm Hybrid plants which are back-crossing to the parents and crossing with themselves, so that there is a continuous intergradation of forms in the population.

hybrid varieties First-generation (F1) progenies from a cross, produced by controlling the pollination, between either two inbred lines, or single crosses, or a single cross and an open-pollinated or a synthetic variety, or two selected clones, seed lines, varieties, or species. A line cross between two closely related inbreds (theoretical coefficient of parentage at least 0.87) is considered equivalent to a line (inbred) variety; the hybrid variety cannot be reproduced from seed of the hybrid generation. Examples of conventional hybrids: `Hybrid-7' spinach, `US13' hybrid corn, `RS-610' hybrid grain sorghum, `Moreton' hybrid tomato, `Comanche' hybrid petunia; examples of varieties that contain substantial numbers of hybrid seeds: `Market Prize' hybrid cabbage, `Valley' hybrid sunflower, `Picadilly' hybrid cucumber.

hybrid variety See hybrid varieties.

hybrid vigor The situation in which the cross of two parents produces hybrids that show increased vigor in comparison to that of either parent.

hydathode (Gr. ydato: to make watery; odos: road, way) n. An epidermal structure, a pore, specialized for secretion, or for exudation, of water, usually from a leaf. Like stomata, hydathodes are surrounded by two crescent-shaped cells but these, unlike guard cells, do not regulate the size of the aperture. Hydathodes are used by the plant to secrete water under conditions in which transpiration is inhibited; for example, when the atmosphere is very humid. This process of water loss is called guttation.

hydnocarpic acid A cyclopentenyl fatty acid.

hydnoid adj. Of a basidia on spines or tooth-like projections.

hydrastine n. An isoquinoline alkaloid.

hydric (Gr. ydraios: aquatic) adj. Characterized by an abundant supply of water. Of, or adapted to, an extremely moist habitat; characterized by, relating to, or requiring an abundance of moisture.

hydrochory (Gr. ydro-: prefix meaning water; khre: to move) n. Dispersal of seed by water

hydrocyanic acid HCN, with its distinctive odour of almonds.

hydroid n. A tracheid-like conductive cell in the central strand of some bryophytes, especially mosses, sometimes also in the costa. Cf. leaf trace.

hydrolysis n. Decomposition of a chemical compound by reaction with water, such as the dissociation of a dissolved salt or the catalytic conversion of starch to glucose.

hydrolyzable tannins Complex esters of gallic acid with a carbohydrate (usually glucose), including gallotannins and ellagitannins; the ester linkages may be hydrolyzed by boiling with dilute hydrochloric acid; usually amorphous, hygoscopic, yellow-brown substances which dissolve in water to form colloidal rather than true solutions.

hydrome n. The sheath or column of hydroid tissue in the stem; the central or axillary strand.

hydrophilic (Gr. ydro-: prefix meaning water; philos: friend, loved) adj. Literally water loving. Hydrophilic compounds dissolve easily in water, and are usually polar.

hydrophilous (Gr. ydro-: prefix meaning water; philos: friend, loved) adj. Growing in water; loving water; pollinated by water. See hydrophily.

hydrophily (Gr. ydro-: prefix meaning water; philos: friend, loved) n. A rare form of pollination in which pollen is carried to a flower by water. It occurs by one of two methods. In Canadian pondweed (Elodea canadensis) the male flowers break off and float downstream until they contact the female flowers. In Zostera, a marine species, the filamentous pollen grains are themselves carried in the water. Cf. anemophily, entomophily.

hydrophobic (Gr. ydrophobia: hydrophobia) adj. 'water fearing'. Hydrophobic compounds do not dissolve easily in water, and are usually non-polar. Oils and other long hydrocarbons are hydrophobic.

hydrophyte (Gr. ydro-: prefix meaning water; phyton: plant) adj., n. Of or pertaining to a hydrophyte. Any plant that lives either in very wet soil or completely or partially submerged in water. Structural modifications of hydrophytes include the reduction of mechanical and supporting tissues and vascular tissue, the absence or reduction of a root system, and specialized leaves that may be either floating or finely divided, with little or no cuticle. Examples of hydrophytes are waterlilies and certain pondweeds. Cf. halophyte, mesophyte; xerophyte.

hydrophytic adj. Adapted to growing in water. See hydrophyte.

hydropote (Gr. ydropots: water drinker) n. A cell or cellgroup found on the lower epidermis of some species such as Nymphaea. These cells are thought to function in the uptake of ions from the water. See also hydropoten.

hydropoten n. The multicellular absorbing (water, mineral salts) structures (hairs) in water plants. See also hydropote.

hydroquinone See hydroquinones.

hydroquinones n. A class of quinones, aromatic phenolic compounds in which two atoms of hydrogen are replaced by two hydroxy groups.

hydrotropic (Gr. ydro-: prefix meaning water; tropos: direction) adj. Turning or tending toward or away from moisture; taking a particular direction with reference to moisture.

hydrotropism (Gr. ydro-: prefix meaning water; tropos: direction) n. Oriented growth or movement in response to water; hydrotropic tendency of growth.

hygrochastic adj. Said of capsules that open only when they are moistened.

hygroline alkaloid Accompanies cocaine in the leaves of Erythroxylon coca.

hygrometric adj. See hygrometry.

hygrometry (Gr. ygros: wet, moist; metron: measure) n. The branch of physics that deals with the measurement of the humidity of air and gases.

hygrophyte (Gr. ygros: wet, moist; phyton: plant) n. A plant that thrives in wet or very moist ground; a hydrophyte, a marsh plant, of wet habitats but not in water.

hygrophytic adj. See hygrophyte.

hygroscopic (Gr. ygros: wet, moist; skope: to aim) adj. Absorbing water and undergoing movements or changes brought about by changes in water content.

hylacolous adj. Dwelling on bark.

hylodophilous adj. Thriving in dry open woodlands.

hymenia See hymenium.

hymenial (Gr. ymn: membrane) adj. Of the hymenium.

hymenium (Gr. ymn: membrane) n. (pl. hymenia) The sporogenous layer in a fungus, composed of asci or basidia often interspersed with various structures, as paraphyses.

Hymenophyllaceae n. A family of the phylum Filicinophyta. lilac.

Hymenoptera n. pl. An order of highly specialized insects with complete metamorphosis that include the bees, wasps, ants, ichneumon flies, sawflies, gall wasps, and related forms, that often associate in large colonies with complex social organization, and that have usually four membranous wings and the abdomen generally borne on a slender pedicel.

hymenopterous adj. Belonging or pertaining to the Hymenoptera, an order of insects having, when winged, four membranous wings, and comprising the wasps, bees, ants, ichneumon flies, and sawflies.

hyoscyamine n. A tropane alkaloid.

hypanthia See hypanthium.

hypanthial adj. See hypanthium.

hypanthium (Gr. hypo, under; anthos: flower) n. (pl. hypanthia) An expansion of the receptacle of a flower that forms a saucer-shaped, cup-shaped, or tubular structure (often simulating a calyx tube) bearing the perianth (sepals and petals) and stamens at or near its rim; the hypanthium is then a cup-shaped extension of the floral axis usually formed from the union of the basal parts of the calyx, corolla, and androecium, commonly surrounding or enclosing the pistils; it may be free from or united to the ovary, as in many Myrtales. Cf. calyx tube.

hypanthodia See hypanthodium.

hypanthodium (Gr. hypo, under; anthos: flower) n. (pl. hypanthodia) An inflorescence with flowers borne on the walls of a capitulum, as in Ficus, Hibiscus, Solanum.

hyperparasite n. A heterotroph obtaining complex nutrients from another organism via the intermediacy of a third, e.g. Monotropa obtains nutrients from trees via the intermediacy of mycorrhizal fungi.

hyperphyll n. The unifacial terete apical portion of a monocot cotyledon, sometimes also visible (small) on other leaves.

hyperplasia (Gr. hyper: above; plasis: molding) n. Abnormal multiplication of cells.

hyperplastic adj. See hyperplasia.

hyperploid (Gr. hyper: above; eidos: form) adj, n. Having a chromosome number that is greater but not a multiple of the diploid number. A hyperploid cell or organism. Cf. aneuploid.

hyperstigma n. A common area in a gynoecium made up of separate carpels where the pollen grains germinate and from which they proceed to any of the individual carpels.

hypertension n. Abnormally high blood pressure and especially arterial blood pressure; the systemic condition accompanying high blood pressure

hypertensive adj., n. Of or characterized by hypertension; causing an increase in blood pressure: a hypertensive medication. A person with or susceptible to hypertension; a drug capable of causing an increase in blood pressure.

hypertrophy (Gr. hyper: above; troph: food) n. Excessive growth due to increase in cell size.

hypha (Gr. yph: tissue, spider web) n. (plural hyphae) A delicate filament in fungi many of which may form either a loose network (mycelium) or a tightly packed interwoven mass of pseudoparenchyma, as in the fruiting body of mushrooms. Hyphae may be branched or unbranched and may or may not possess cross walls. The cell wall consists of either fungal cellulose or a nitrogenous compound called chitin. The cell wall is lined with cytoplasm, which often contains oil globules and glycogen, and there is a central vacuole. The hyphae produce enzymes that in parasitic fungi digest the host tissue, and in saprotrophic fungi digest dead organic matter.

hyphae See hypha

hyphal (Gr. yph: tissue, spider web) adj. Related to an hypha.

hypnoid adj. Having a complete peristome; occasionally used to refer to a moss with a pleurocarpous habit, e.g. Hypnum cupressiforme.

hypnosperm (Gr. ypnos: sleep; sperma: seed) n. A hypnospore.

hypnosporangia See hypnosporangium.

hypnosporangium (Gr. ypnos: sleep; spora: seed; aggeion: bowl, container) n. (pl. hypnosporangia) A sporangium containing hypnospores.

hypnospore (Gr. ypnos: sleep; spora: seed) n. A thick-walled, asexual, resting spore.

hypo- (Gr. ypo: below, under) prefix. Meaning beneath or under.

hypoallergenic adj. Having a decreased tendency to provoke an allergic reaction.

hypobasal adj. Of the the lower initial (cell) of the two-celled embryo.

hypochil (Gr. ypo: below, under; kheilos: lip) n. The basal portion of the lip of some flowers of the Orchidaceae. Also hypochile.

hypochile See hypochil.

hypochilia See hypochilium.

hypochilium (Gr. ypo: below, under; kheilos: lip) n. (pl. hypochilia) See hypochil.

hypocotyl (Gr. ypo: below, under; kotyldon: cavity, hollow) n. The region of the stem beneath the stalks of the seed leaves (cotyledons) and directly above the young root of an embryo plant. It grows rapidly in seedlings showing epigeal germination and lifts the cotyledons above the soil surface. In this region (the transition zone) the arrangement of vascular bundles in the root changes to that of the stem. Cf. epicotyl.

hypocotylous See hypocotyl.

hypocrateriform (Gr. ypo: under; krater: bowl; L. forma: shape) adj. Platter-shaped; salver-shaped; hypocraterimorphous. Syn. salverform. adj. Hypocraterimorphous; salver-shaped.

hypocraterimorphous adj. Salver-shaped; having a slender tube, expanding suddenly above into a bowl-shaped or spreading border, as in the blossom of the phlox and the

hypoderm n. See hypodermis.

hypoderma n. See hypodermis.

hypodermal adj. Of one or more layers of differentiated cells beneath the epidermis of the stem. Cf. hypodermis, cortex.

hypodermis (Gr. ypo: under; derma: skin) n. The outermost layer of cells in the plant cortex, lying immediately below the epidermis. These cells are sometimes modified to give additional structural support or to store food materials or water. After the loss of the piliferous layer of the root the hypodermis takes over the protective functions of the epidermis. Syn. exodermis, hypoderm, hypoderma.

hypogaeal See hypogeal.

hypogaeous See hypogeal

hypogeal (Gr. ypo: under; g: earth) adj. Describing seed germination in which the seed leaves (cotyledons) remain below ground. Examples of hypogeal germination are seen in oak and runner bean. Cf. epigeal. Describing fruiting bodies that develop underground, such as truffles and peanuts. Syn. hypogaeal, hypogaeous, hypogeous.

hypogenous (Gr. ypo: under; genna: to produce) adj. Growing beneath, or under the surface, as fungi on leaves.

hypogeous See hypogeal.

hypoglycaemic adj. See hypoglycemic.

hypoglycemia n. An abnormally low level of glucose in the blood.

hypoglycemic adj. Of or relating to hypoglycemia; as an agent lowering the concentration of glucose in the blood: a hypoglycemic drug. Of or relating to low blood sugar. Also hypoglycaemic.

hypogonianthus n. (pl. hypogonianthi) A three keeled perianth with two lateral and one ventral or postical keels. Cf. epigonianthus.

hypogynous (Gr. ypo: under; gyn: female) adj. Situated on the receptacle beneath the ovary and free from it and from the calyx; having the petals and stamens so situated; inserted below the gynoecium, and not adherent; immediately below thew oogonium; the ovary thus said to be superior. Cf. perigynous, epigynous.

hypogyny (Gr. ypo: under; gyn: female) n. A floral arrangement in which the ovary is superior, i.e. it arises from the receptacle above the sepals, petals, and stamens. The perianth and stamens are said to be hypogynous with respect to the ovary, as seen in the tulip. Cf. epigyny, perigyny.

hypolithic (Gr. ypo: under; lithos: stone) adj. Growing under rock, as a plant.

hyphomycete n. A mitosporic fungus forming a mycelium with or without pigment.

hyponastic adj. See hyponasty.

hyponasty (Gr. ypo: under; nastos: pressed) n. In plant physiology, the state in which more vigorous growth occurs in the lower surface of an organ, such as a young fern frond, causing an upward curvature. Cf. epinasty.

hypophleodal (Gr. ypo: under; phloios: bark; eidos: form) adj. Living or growing beneath bark, as a lichen. Syn. hypophleodeous, hypophleodic.

hypophleodeous See hypophleodal.

hypophleodic See hypophleodal.

hypophyllous (Gr. ypo: under; phyllon: leaf) adj. Growing under the surface of leaves, as a fungus.

hypophysis n. (pl. hypophyses) A strongly differentiated, sterile neck at the base of the capsule, between seta and urn, e.g. Trematodon, Splachnum. Also apophysis.

hypoploid (Gr. ypo: under; eidos: form) adj, n. Haing a chromosome number that is less than not the diploid number. A hypoploid cell or organism. Cf. aneuploid.

hypopodia See hypopodium

hypopodium (Gr. ypo: under; pous, podos) n. (pl. hypopodia) The basal portion of a petiole.

hypostase n. Of the ovule or young seed, with the tissue distinctly diffent from surrounding cells at the chalazal region of the ovule, usually lignified or suberised and immediately interior to or above the chalazal vascular supply and interior to the integuments.

hypostatic adj. Of the lobules of male bracts overlapping ventrally; imbricate; Cf. epistatic, epistasis.

hypotension n. Abnormally low blood pressure.

hypotensive adj., n. Of or characterized by hypotension; causing a reduction in blood pressure: a hypotensive drug. A person with or susceptible to hypotension.

hypothalli See hypothallus.

hypothallus (Gr. ypo: under; thallos: young shoot) n. (pl. hypothalli) A layer of hyphae, often dense and more or less woolly or spongy, without photobiont, at margins or below thallus, often black or dark brown in Anzia, Pannoparmelia and Pannariaceae.

hypothecia See hypothecium.

hypothecium (Gr. ypo: under; thk: case, box) n. (pl. hypothecia) The layer of hyphal tissue directly beneath the hymenium.

hypotriploid adj., n. A triploid (3x) lacking one or more chromosomes, as in instances in which 2n = 20 instead of the expected 21 derived from a basic (x) number of 7.

hypsophyll A leaf inserted at high levels on plant, shoot or innovation, e.g. a bract, normally of little use.

hysteranthous (Gr. ysteros: after, behind; anthos: flower) .dj. With the leaves appearing after the flowers.