ob- (L. ob: for, because, in exchange of prefix. Meaning towards, to, over, on, reversely, inversely.

obclavate (L. ob: inversely: clava: club) adj. Inversely clavate, i.e. club-shaped, but with the attachment at the broad end.

obcompressed adj. Flattened from back to front rather than from side to side, as in the fruits of pennycress or peppergrass.

obconic See obconical.

obconical (L. ob: inversely: conus: cone: club) adj. Inversely conical, i.e. cone-shaped but attached at the narrower end. Syn. obconic.

obconically adv. See obconical.

obcordate (L. ob, inversely; cor, cordis; heart) adj. Of a leaf blade, broad and notched at the tip; heart-shaped but attached at the pointed, narrower end. Syn. obcordiform/

obcordiform (L. ob: inversely; cor, cordis; heart; forma: shape) See obcordate.

obcuneate adj. Like cuneate, but with the point of attachment at the broad end.

obdeltoid (L. ob: inversely; Gr. the letter delta; eid˘: to ressemble) adj. Deltoid, but with the attachment at the pointed end.

obdiplostemonous (L. ob: over; Gr. diploos: double; stŕm˘n: thread) adj. Having two whorls of stamens, the outer whorl opposite the petals and the innery whorl opposite the sepals; e.g. the androecium of Vaccinium angustifolium.

obelliptic See obelliptical.

obelliptical (L. ob: inversely; Gr. elleipsis: omission) adj. Almost elliptic, but with the distal end somewhat larger than the proximal end.

obhaplostemonous adj. of an androecium with as many stamens as petals, the former borne in a single whorl opposite the petals or inner whorl of tepals.

oblanceolate adj. (L. ob: inversely; lancea: spear, pike, lance) Shaped like a lance point reversed, that is, having the tapering point next to the leafstalk, i.e. attached at the narrower end.

oblate adj. Spheroidal and flattened at the poles; wider than long.

obligate (L. obligatus: mandatory) adj. Restricted to particular conditions, circumstances or particular way of life; for example, an obligate parasite is unable to survive without a host. Opposite: facultative.

oblique (L. obliquus: oblique) adj. Of a leaf or leaflet, larger on one side of the midrib than on the other, i.e. asymmetrical but almost symmetrical; having unequal sideds; slanting.

obloid n. A three-dimensional shape with short, parallel sides and rounded ends, as if composed of two hemispheres linked together by a very short cylinder. adj. In the shape of a short cylinder (not above twice as long as wide). Used here with reference to the shape of flower-heads. Synonyme : oblongoid.

oblongoid See obloid.

oblong (L. oblongus: lengthened) adj. Elliptical and from two to four times as long as broad; having the length greater than the width but not many times greater, and the sides parallel; broadly elliptical with blunt ends.

obovate (L. ob: reversely; ovum: egg) adj. Inversely ovate; having the shape of the longitudinal section of an egg, with the broad end at the top, as some leaves.

obovoid (L. ob: inversely; ovum, egg; Gr. eidos: shape) adj. Inversely ovoid; roughly egg-shaped, with narrow end downwards; said of some fruits.

obpyramidal adj. Shallowly triangular with the attachment at the point rather than the middle of the flat side.

obpyriform adj. pear-shaped but broadest above the middle.

obsolescent (L. obsolescere, to go out of use; [ob, against; solere, to be accutomed]) adj. Non-functional but not reduced to a rudiment.

obsolete (L. obsolescere: to go out of use) adj. Rudimentary or not evident; applied to a structure that is almost suppressed; vestigial.

obturator n. An outgrowth of the funicle (commonest), placenta, or integument, etc., that forms a bridge between the micropyle and other tissues and is believed to faciltate fertilisation.

obtuse (L. obtusus: blunt) adj. With blunt or rounded end, the converging edges separated by an angle greater than 90 degrees.

obverse adj. Describing a leaf that is narrower at the base than at the apex.

obvolute adj. Of a vernation in which two leaves are overlapping in the bud in such a manner that one-half of each is external and the other half is internal, i.e. each leaf both overlaps the next and is in turn overlapped by the one before.

ocellate See ocellated.

ocellated adj. Having an ocellus or ocelli; resembling an ocellus; having spots. Also ocellated.

ocelli See ocellus.

ocellus (L. ocellus: little eye) n. (pl. ocelli) An eye-like marking, as in a spot of color encircled by a band of another color; a spot of colour surrounded by a ring of a different colour on the wing of a butterfly etc.; in bryophytes, an idioblastic leaf cell having one large oil body and lacking chloroplasts, also found in underleaves, bracts and perianths of certain leafy liverworts (Frullania, certain Lejeuneaceae.

Ochoan n. The final series in the Permian of N. America, underlain by the Guadalupian, overlain by the Triassic (see Scythian), and roughly contemporaneous with the upper Kazanian and Tatarian Stages.

ochraceous (L. ochra: ochre) adj. Ochre-colored, i.e. from pale yellow to orangish or reddish yellow.

ochrea (pl. ochreae). See ocrea.

ochreae See ochrea.

ochreoleucous See ochroleucous.

ochroleucous adj. Yellowish white; having a faint tint of dingy yellow. Also ochreoleucous.

ocrea (L. ocrea: greave, gaiter, legging) n. (pl. ocreae) A tubelike covering around some stems, a sheath, formed from two stipules, encircling the node, especially of plants of the Polygonaceae; in bryophytes, the flared apex of the vaginula, forming a collar around the base of the seta, as in Macrocoma.

ocreae See ocrea.

ocreate (L. ocreatus: wearing gaiters) adj. Having an ocrea or ocreae; sheated; with sheathing stipules.

ocreola (diminutive of L. ocrea: greave, gaiter) n. (pl. ocreolae). A minute stipular sheath around the secondary divisions of the infloresce in some members of the Polygonaceae.

ocreolae See ocreola.

ocreolate (diminutive of L. ocreatus: wearing gaiters) adj. With minute sheathing stipules; often applied to bract bases.

octamerous (Gr. oktamerŕs: composed of eight parts) adj. Of flowers having eight in each whorls.

octandrous (Gr. okt˘: eight; anŕr, andros: male) adj. With eight stamens.

octo- (L. octo: eight or Gr. okt˘: eight) prefix. Meaning eight.

octofarious adj. Eight-ranked.

octogynous (Gr. okt˘: eight; gynŕ: female) adj. With eight pistils or styles.

octolocular (L. octo: eight; loculus: little spot, little box) adj. With eight locules.

octopetalous adj. (Gr. okt˘: eight; petalon: leaf) With eight petals.

octoploid adj., n. Having eight haploid sets of chromosomes in a body cell. An octoploid organism.

octoradiate (L. octo: eight; radiatus; with rays) adj. With eight ray flowers.

octosepalous (Gr. okt˘: eight; skepas: covering, shelter; [pe]talon: leaf) adj. With eight sepals.

octostemonous (Gr. okt˘: eight; stŕm˘n: thread) adj. With eight stamens.

octostichous (Gr. okt˘: eight; stikhos: line, row) adj. In eight ranks or rows.

odd pinnate See odd-pinnate.

odd-pinnate adj. Pinnately compound with a terminal leaflet (or tendril) rather than a pair of leaflets (or a tendril), so that there is an odd number of leaflets; this is usually easily determined because there is a single terminal leaflet (or a terminal tendril). Also odd pinnate.

odoriferous (L. odor, odoris: smell, scent, odor; ferre: to carry) adj. With a distinct odor, especially a fragrant one.

oedema See edema.

oestral adj. See oestrus. Also estral.

oestrum n. A regularly occurring period of sexual receptivity in most female mammals, except humans, during which ovulation occurs and copulation can take place. Also oestrus, estrous, estrum and estrus.

oestrus n. A variant of estrum, oestrum oestrus and estrus.

officinal adj., n. Readily available in pharmacies; not requiring special preparation. Recognized by a pharmacopoeia: an officinal herb. An officinal drug.

offset n. A short, often prostrate, shoot originating near the ground at the base of another shoot.

offshoot n. A shoot or branch arising from a main stem.

off-type n. A plant or seed that deviates in one or more characteristics from that described as being usual for the strain or variety. Any seed or plant not a part of the variety in that it deviates in one or more characteristics of the variety as described and may include seeds or plants of other varieties; seeds or plants resulting from cross-pollination by other kinds or varieties; seeds or plants resulting from uncontrolled self-pollination during production of hybrid seed; and segregates from any of the above plants.

oidia See oidium.

oidium n. (pl. oidia) Thin-walled cell that functions as a spore or in sexual processes in fungi.

oil (L. oleum: olive oil, oil) n. There are three types of oil: lipids (see fats and oils), essential oils, and mineral oil (petroleum).

oil body A membrane-bound, terpene-containing organelle unique to the cells of liverworts.

oil cell An idioblastic cell characterized by a very large oil body, common in thalloid liverworts; e.g. Marchantia.

oil dots See oil glands.

oil droplet Any minute spherule of oil within the cell cytoplasm; not associated with an organelle.

oil glands Small structures embedded in a leaf or other organ, secreting a volatile oil, mostly visible as small translucent dots against a strong light; usually making the organ aromatic when crushed.

oil tube Narrow ducts in the walls of the fruits of many members of the Umbelliferae (Apiaceae) containing volatile oils.

Old Red Sandstone Continent The continental facies of the Devonian in the British Isles. It is characterized by red sandstones and conglomerates which were deposited under terrestrial conditions.

oleaginous (L. oleaginus: from the olive tree) adj. Oily; oil-producing.

oleiferous (L. oleum: olive oil, oil; ferre: to carry) adj. Oil-bearing.

oleoresin n. A naturally occurring mixture of an oil and a resin extracted from various plants, such as pine or balsam fir.

oleoside n. A type of secoiridoid monoterpene.

oligandrous (Gr. oligos: a little; anŕr, andros: male) adj. With few stamens.

oligo- (Gr. oligos, a little) prefix. Meaning few.

oligocarpic See oligocarpous.

oligocarpous (Gr. oligos: a little; karpos: fruit) adj. Bearing less than the typical amount of fruit. Syn. oligocarpic.

Oligocene (Gr. oligos: a little; kainos: new) n. An epoch (35.4 to 23.3 million years ago) of the Tertiary Period. It follows the Eocene and precedes the Miocene Epochs. The Oligocene Epoch comprises the Rupelian and Chattian Ages.

oligogenic adj., n. Of a major gene, one or a few mendelian determinants.

oligomerous (Gr. oligos: a little; meros: part) adj. With less than the typical number of parts.

oligokaryotic adj. Of a hyphal compartment with 3 to 10 nuclei.

oligolecty n. Refers to bees that exhibit a narrow, specialized preference for pollen sources, typically to a single genus of flowering plants. The preference may occasionally extend to multiple genera within a single plant family, or be as narrow as a single plant species.

oligolege n. A pollinator that exhibit a narrow, specialized preference for pollen sources, typically to a single genus of flowering plants. See oligolecty.

oligophyllous (Gr. oligos: a little; phyllon: leaf) adj. With few leaves.

oligoporous adj. With few pores.

oligospermous (Gr. oligos: a little; sperma: seed) adj. With few seeds.

oligotrophe n. See oligotrophic.

oligotrophic (Gr. oligos: a little; trophŕ: food) adj. Of a lake characterized by a low accumulation of dissolved nutrient salts, supporting but a sparse plant and animal life, and having a high oxygen content owing to the low organic content.

oligotrophy (Gr. oligos: a little; trophŕ: food) n. The state of being oligotrophic.

olivaceous (L. oliva: olive) adj. Olive-green; olive-like.

olliform (L. olla: pot, jar) adj. In the shape of a flower-pot; a truncated cone.

ombrotrophe n. See ombrotrophic.

ombrotrophic adj. Receiving nutrients solely from rain water.

one-foliolate A compound leaf reduced to a single leaflet, usually recognized by the articulated or jointed `petiole', which is in fact a petiole plus a petiolule. Syn. unifoliolate.

one-ranked adj. Said of leaves borne singly and in a single orthostichy up the stem.

ontogenetic adj. Related to ontogeny.

ontogeny (Gr. ontos: being; genna˘: to produce) n. Biologists' term for the origin and whe development of a single organism, i.e. the sequence of stages through which it passes during its lifetime, from the fertilized egg through to maturity. The ontogeny of language is therefore its development in children, as opposed to its 'phylogeny', which is its evolution in our species. It has been suggested that ontogeny recapitulates phylogeny, i.e. the stages of development, especially of the embryo, reflect the evolutionary history of the organism. This idea is now discredited.

oocyst n. Desiccation-resistant thick-walled structure in which sporozoans are transferred from host to host.

oocyte (Gr. ˘on: egg; kytos: what covers) n. A female germ cell (primary oocyte) that gives rise by meiosis to a polar body and a haploid cell (secondary oocyte), which in turns gives rise to a second polar body and an ootid.

oogamous adj. Characterized by or having small motile male gametes and large nonmotile female gametes.

oogamy n. When a male gamete is flagellated but the larger female gamete is not, e.g. the mosses.

oogonia See oogonium.

oogonium (Gr. ˘on: egg; gonos: generation) n. (pl. oogonia) The female sexual organ in Carophytes, of algae and fungi.

Oomycota (Gr. ˘on: egg; mykŕs, mykŕtos: fungus) n. A phylum of the Protoctista that includes the water moulds, downy mildews, and potato blight (Phytophthora), formerly classified as a class of fungi (Oomycetes). They are coenocytic and the cell wall is made of cellulose. Oomycotes are either saprotrophic or parasitic; they feed by extending hypha-like threads into the food source or host's body. Asexual reproduction is by means of flagellated zoospores, which are released from a sporangium. Sexual reproduction involves the fusion of an antheridium and an oogonium and results in the production of a zygote, which can develop a wall of chitin and become a resistant oospore.

oophore (Gr. ˘on: egg; phorń carrying) n. An oophyte. Also o÷phore.

o÷phore See oophore.

oophyte (Gr. ˘on: egg; phyton: plant) n. The gametophyte of a fern, moss, or liverwort, resulting from the development of a fertilized egg. Also o÷phyte.

o÷phyte See oophyte.

oosphere (Gr. ˘on: egg; sphairń sphere) n. The nonmotile female gamete in plants and some algae. In angiosperms (flowering plants) it is a cell in the embryo sac of the ovule. In other plants it is situated in an archegonium. In algae, such as Fucus, the oosphere is protected by an oogonium until it is shed into the water prior to fertilization. Many oospheres store food in the form of starch or oil droplets. Syn. egg cell, ovum. Also o÷sphere.

o÷sphere See oosphere.

oospore (Gr. ˘on: egg; sporń seed) n. A zygote that is produced as a result of oogamy in certain algae and fungi, corresponding to angiosperm seeds. It contains food reserves, develops a protective outer covering, and enters a resting phase before germination. Cf. zygospore. Also o÷spore.

o÷spore See oospore.

ootid (Gr. ˘on: egg) n. The cell that results from the meiotic division of an oocyte and matures into an ovum. Also o÷tid.

o÷tid See ootid.

opaque adj. Not transparent or translucent.

Operational Taxonomic Unit The definitions or names of the taxa included in a phylogenetic analysis.

opercula See operculum.

operculate adj. With an operculum.

operculum (L. operculum: lid) n. (pl. opercula) In mosses, a lidlike structure, the upper portion of a circumscissile capsule, usually separated from the mouth by an annulus to open the capsule, which on detatchment permits the spores to escape.

operon n. A set of structural genes controlled by an adjacent site on a strand of DNA; their activity is manifested in the controlled synthesis (transcription) of mRNA; may be catabolite-sensitive or insensitive.

Ophioglossaceae n. A family of the phylum Filicinophyta.

ophthalmia n. Inflammation of the eye, especially of the conjunctiva.

opiate (L. opium: opium) n. One of a group of drugs derived from opium, an extract of the poppy plant Papaver somniferum that depresses brain function (a narcotic action). Opiates include morphine and its synthetic derivatives, such as heroin and codeine. They are used in medicine chiefly to relieve pain, but the use of morphine and heroin is strictly controlled since they can cause drug dependence and tolerance.

opposite (L. oppositus: opposed, put in front) adj. Said of leaves or bracts occurring two at a node on opposite sides of the stem. Said of flower parts when one part occurs in front of another, as a stamen in front of a petal. Having one organ vertically above another; superimposed. Cf. alternate.

orbicular (L. orbiculus: little wheel) adj. Circular or nearly so; round or shield-shaped leaf with petiole attached to center. Ex: leaf of common nasturtium.

orbiculate See orbicular.

orbicule See orbicules.

orbicules n. Minute granules of sporopollenin secreted by the tapetum, sometimes found on pollen grains.

order n. A taxonomic grouping of families believed to be closely related (sometimes a single family with no apparent close relatives).

Ordovician n. The second (510 to 439 millions years ago) of six periods that constitute the Palaeozoic Era, named after an ancient Celtic tribe, the Ordovices. The Ordovician follows the Cambrian and precedes the Silurian. It is noted for the presence of various rapidly evolving graptolite genera and of th e earliest jawless fish.

orgadophilous adj. Thriving in meadows.

organ (Gr. organon: organ) n. A differentiated part or member having a specific function. A collection of tissues which performs a particular function or set of functions in an plant's body; the leaf, stem, and root are three organs found in many plants; organs are composed of tissues.

organelle (diminutive of Gr. organon: organ) n. A minute structure within a eukaryotic cell that has a particular function. Examples of organelles are the nucleus, mitochondria, and lysosomes.

orifice n. An opening through which spores escape from the capsule.

ornithophillous See ornithophilous.

ornithophilous (Gr. ornis, ornithos: bird; philos: friend, loved) adj. Of flowers pollinated by birds. Also ornithophillous.

orobanchin See orobanchoside.

orobanchoside n. A phenylpropanoid, an ester of caffeic acid, two molecules and two sugar molecules also being involved. Also orobanchin.

orophilous (Gr. oros: mountain) adj. Growing in mountainous areas.

ortet n. The original ancestor of a vegetative clone.

orthocladous (Gr. orthos: straight; klados: branch) adj. With straight branches.

orthopterous (Gr. orthos: straight; pteron: wing) adj. Straight-winged.

orthosermous (Gr. orthos: straight; sperma: seed) adj. A term applied to those fruits of the Umbelliferae which have the seed straight.

orthostichous (Gr. orthos: straight; stikhos: line, row) adj. With parts arranged in straight ranks or rows; e.g. the leaves of Phyllogonium.

orthostichy (Gr. orthos: straight; stikhos: line, row) n. A vertical rank or row; an arrangment of members, as leaves, at different heights on an axis so that their median planes coincide.

orthotropic (Gr. orthos: straight; tropos: direction) adj. Of, pertaining to, or exhibiting an essentially vertical growth habit; the main shoot of a tree is often orthotropic; many of the upper branches of the American elm (Ulmus americana) are orthotropic, giving the tree its characteristic vase shape.

orthotropism (Gr. orthos: straight; tropos: direction) n. Orthotropic tendency or growth.

orthotropous (Gr. orthos: straight; tropos: direction) adj. Of an ovule, erect so that the micropyle points away from the placenta, i.e. with the chalaza at the evident base and the micropyle at the opposite extremity.

Osagean n. A series in the Mississippian of N. America, underlain by the Kinderhookian, overlain by the Meramecian, and roughly contemporaneous with the Ivorian Stage of the Tournaisian Series and the Chadian Stage of the Visean Series.

osmosis n. The tendency of a fluid, usually water, to pass through a semipermeable membrane into a solution where the solvent concentration is higher, thus equalizing the concentrations of materials on either side of the membrane. The diffusion of fluids through membranes or porous partitions.

Osmundaceae n. A family of the phylum Filicinophyta.

osseous (L. osseus: bony) adj. Bony, ressembling bones.

ossiculus (L. ossiculum: little bone) n. The stone or pit of a drupe; a pyrene.

ossified (L. os, ossis: bone) adj. Becoming bony.

ostiolar adj. See ostiole.

ostiolate adj. See ostiole.

ostiole (diminutive of L. ostium: door) n. An opening or pore, e.g. (in Moraceae) at the apex of a fig, or (in certain fungi, algae and lichens) at the apex of a perithecium, and through which either spores or gametes are released. An ostiole occurs, for example, in the perithecium of ascomycete fungi (see ascocarp) and in the conceptacle of brown algae.

ostracod (Gr. ostrakon: shell, scale) n. Any of the crustacean of the class Ostracoda. See Ostracoda.

Ostracoda (Gr. ostrakon: shell, scale) n. A class of crustaceans that are typical Arthropoda but laterally compressed and enclosed within a bivalved carapace. This pair of calcareous valves is an integral part of the epidermis and is closed by a series of muscles that leave scars (see Muscle Scar) on the valve interiors. The appendages are typically biramous but may be modified for digging, swimming, etc. The group includes herbivores, carnivores, and scavengers, and occurs in most aquatic habitats. Most are small (less than 1 mm long) and more than 10 000 species have been described, occurring from the Cambrian to the present day. The biological classification of recent forms is based on the soft-part anatomy and fossil forms are classified by the nature of the preserved carapaces. Such characters as the nature of the hinge, the pattern of the muscle scars, as well as overall shape and ornamentation are all used in species determination. Ostracods have considerable stratigraphic use, and are also used to demonstrate variations in salinity and fluctuations in the positions of shorelines.

OTU See Operational Taxonomic Unit.

outbreeding n. The random mating of individuals. Also outcrossing, cross-pollination.

outbreeder n. See outbreeding, cross-pollination.

outcross n., vt. To transfer pollen from the anthers of the flowers of one plant to the stigma of the flower of another plant. The mating of a hybrid with a third parent; also an offtype plant resulting from pollen of a different sort contaminating a field of usually self-pollinated plants.

outcrossed See outcross.

outcrossing Fertilizing between two different plants. The practice of introducing unrelated genetic material into a breeding line. It increases genetic diversity, thus reducing the probability of all individuals being subject to disease or reducing genetic abnormalities(only within the first generation). It actually can serve to increase the number of individuals who carry a disease recessively. See also outbreeding.

outgroup n. In a cladistic analysis, any taxon used to help resolve the polarity of characters, and which is hypothesized to be less closely related to each of the taxa under consideration than any are to each other.

ova See ovum.

oval (L. ovum: egg) adj. Twice as long as broad, widest at the middle, both ends rounded; broadly elliptic, the width over one-half the length.

ovary (L. ovum: egg) n. The hollow enlarged base of the carpel (pistil) of a flower, containing one or more ovules. After fertilization, the ovary wall develops into the fruit enclosing the seeds. In some species, the carpels are fused together to form a complex ovary.

ovate (L. ovum: egg) adj. Having the shape of a longitudinal section of an egg; egg-shaped and attached by the broader, wider end.

overall similarity A method by which organisms that share the most similarities are grouped together; characters are not distinguished as to whether they are primitive or derived or whether they are evolutionary meaningful; cf. numerical taxonomy (phenetics), phylogenetic systematics (cladistics).

overdominance Said when the heterozygote is superior to either homozygote.

overstory n. The uppermost layer of foliage that forms a forest canopy.

oviform (L. ovum: egg; forma: shape) adj. Shaped like an egg; ovoid.

oviparous (L. ovum: egg; parere: to produce) adj. Egg-laying; producing eggs which hatch after leaving the body of the female; germinating while still attached to the parent plant; for example, mangrove.

ovoid (L. ovum: egg; Gr. eid˘: to look like) adj. Egg-shaped; a solid with an oval outline.

ovoidal adj. See ovoid.

ovulate (L. ovum: egg) adj. With ovules. Of or pertaining to ovules; producing ovules.

ovule (diminutive of L. ovum: egg) n. A structure in seed plants, the part of the female reproductive organs that consists of the megasporangium (nucellus), megaspore (embryo sac), and integuments (food store and coat) and develops into a seed after fertilization. The ovules of gymnosperms are situated on ovuliferous scales of the female cones while those of angiosperms are enclosed in the carpel.

ovuliferous (diminutive of L. ovum: egg; L. ferre: to carry) adj. Bearing ovules (e.g. applied to scales in a megasporangiate cone in gymnosperms).

ovulode (L. ovum: egg; eid˘: to look like) n. Sterile structures on the placenta.

ovum (L. ovum: egg) n. (plural. ova). See oosphere.

oxalate n. A salt or ester of oxalic acid. Also ethanedioate.

oxalic acid COOH - COOH, a common organic acid in plants, oaxalte itself is usually found in plants as calcium oxalate.

oxygenase n. Any enzyme that oxidizes a substrate by transferring the oxygen from molecular oxygen as in air) to it. The oxygenases form a class of oxidoreductases.

oxylophyte (Gr. oxos: vinegar; phyton: plant) n. A plant growing on acidic soils, of humus rich (acid) habitats.

oxytocic adj. n., (A drug) that induces labor by stimulating contractions of the muscles of the uterus. See also oxytocin.

oxytocin n. A hypothalamic hormone stored in the posterior pituitary, which has uterine-contracting and milk-releasing actions.