abaxial: of the side or surface of an organ, facing away from the axis. cf. adaxial.

abscission: the normal shedding from a plant of an organ that is mature or aged, e.g. a ripe fruit, an old leaf. adj. abscissile.

acarodomatia: domatia adapted to provide shelter to beneficial mites.

accessory fruit: a fruit, or group of fruits derived from one flower, in which the conspicuous, fleshy portion develops from the receptacle and is shed with the true fruit(s) attached.

accrescent: continuing to increase in size after maturity, as the calyx of some plants after flowering.

accumbent: of the orientation of an embryo, with the radicle lying against the edges of the two cotyledons.

achene: a dry, indehiscent fruit formed from a superior ovary of one carpel and containing one seed which is free from the pericarp (often applied, less correctly, to the one-seeded fruits of Asteraceae). cf. cypsela.

acicle: a slender, stiff, needle-like prickle. adj. acicular.

aciculate: finely scored on the surface, as if scratched by a pin.

acrodromous: of leaves, with two or more primary or strongly developed secondary veins running in convergent arches towards the apex. Arches not recurved at base. brochidodromous, eucamptodromous, semicraspedodromous.

acropetal: arising or developing in a longitudinal sequence beginning at the base and proceeding towards the apex. cf. basipetal.

acroscopic: facing towards the apex. cf. basiscopic.

acrostichoid: of sporangia, densely covering the abaxial surface of the fertile frond, i.e. not in distinct groups; of ferns, having the sporangia arranged as above.

acrotonic: of flowering seasonal growth units (seasonal shoots), producing leaves below the inflorescence, cf. basitonic.

actinomorphic: of a flower or calyx or corolla, radially symmetrical; symmetrical about more than one plane passing through the axis of the flower. cf. peloric, zygomorphic.

aculeate: prickly.

acumen: a long, tapering point.

acuminate: tapering gradually to a protracted point.

acute: terminating in a distinct but not protracted point, the converging edges separated by an angle less than 90 degrees.

adaxial: of the side or surface of an organ, facing towards the axis. cf. abaxial.

adnate: fused to an organ of a different kind, e.g. applied to a stamen fused to a petal. cf. connate.

adventitious: arising in abnormal positions, e.g. roots arising from the shoot system, buds arising elsewhere than in axils of leaves.

adventive: introduced to an area recently. cf. introduced, naturalised.

aerenchyma: tissue incorporating large, gas-filled spaces interspersed with the cells in a characteristic pattern.

aestivation: the arrangement of sepals and petals or their lobes in an unexpanded flower bud. cf. vernation.

aggregate fruit: a cluster of fruits formed from the free carpels of one flower. cf. syncarp.

albumen: = endosperm.

allantoid: sausage-shaped.

allopatric: of distributions of two taxa or populations, having different ranges of distribution. cf. parapatric, sympatric.

alternate: of leaves or other lateral organs, borne singly at different heights on the axis; of floral parts, on a different radius, e.g. describing the position of stamens with respect to petals. cf. opposite.

alternitepalous: of floral parts, inserted alternately with the tepals.

alveolate: pitted or honeycombed on the surface.

amplexicaul: of a leaf base, stem-clasping.

anastomosis: fusion to form a network, e.g. of veins in a leaf blade.

anatropous: of an ovule, inverted so that the micropyle faces the placenta.

anauxotelic: applied to inflorescences, parts of inflorescences or to axes that do not end in a flower, and in which growth does not continue beyond the flowering region, cf. auxotelic.

androdioecious: having bisexual flowers and male flowers, on separate plants.

androecium: the stamens of one flower collectively.

androgynophore: a stalk bearing both the androecium and gynoecium of a flower above the level of insertion of the perianth.

androgynous: having male and female flowers in the same inflorescence.

andromonoecious: having bisexual and male flowers, on the same plant.

androphore: a stalk bearing the androecium.

anemophilous: pollinated by wind.

angiosperm: a seed-bearing plant whose ovules, and hence seeds, develop within an enclosed ovary. cf. gymnosperm.

angustiseptate: with narrow partitions, cf. latiseptate.

annual: a plant whose life span ends within one year after germination. cf. biennial, perennial.

annular: arranged in or forming a ring.

annular corona: raised fleshy tissue, usually in a ring, on the corolla around the base of the staminal column but not closely adnate to it.

annulus: a ring; in ferns, the elastic ring of cells, forming part of the sporangium wall, that initiates dehiscence.

anterior: of floral organs, on the side of the flower farthest from the axis. cf. posterior.

anther: the pollen-bearing part of a stamen. cf. filament.

antheridium: the fertile organ of a male gametophyte or the male organ of a bisexual gametophyte, in which male gametes are formed. cf. archegonium.

anthesis: the time of opening of a flower.

anthocarp: a false fruit consisting of the true fruit and the base of the perianth, as in Nyctaginaceae.

antipetalous: inserted in front of the petals; opposite the petals.

antisepalous: inserted in front of the sepals; opposite the sepals.

antrorse: bent, and pointing towards the apex. cf. retrorse.

apetalous: without petals.

apical: of a placenta, at the top of the ovary.

apiculum: a short, abrupt, flexible point, adj. apiculate.

apocarpous: of a gynoecium, consisting of two or more carpels which are free from one another or almost so.

apomict: a plant that produces viable seed without fertilisation.

apomorphic: of a character, derived. cf. autoapomorphic, pleisiomorphic, synapomorphic.

appendage: a structure arising from the surface or extending beyond the tip of another structure.

appressed: pressed closely against a surface (or another organ) but not united with it.

aquatic: living in or on water for all or a substantial part of the life span (generally restricted to fresh/inland waters).

arborescent: resembling a tree (applied to non-woody plants attaining tree height and to shrubs tending to become tree-like in size). cf. dendroid.

archegonium: the fertile organ of a female gametophyte or the female organ of a bisexual gametophyte, in which female gametophytes are formed. cf. antheridium.

arcuate: curved like a bow.

areole: a space between the threads of a net; in Cactaceae, a cluster of hairs/spines/bristles borne at the node of a leafless stem; in Mimosaceae (for example), a distinct, oblong or elliptical area on the face of a seed, bounded by a fine line; on leaf laminas: the space bounded by the finest veins. adj. areolate.

aril: a structure partly or wholly covering the testa of a seed and formed by expansion of the funicle. adj. arillate.

aristate: having a stiff, bristle-like awn or tip.

aristulate: having a small awn.

article: a segment of a jointed stem, or of a fruit with constrictions between the seeds.

articulate: jointed; having joints where separation may occur naturally; of a stem, having nodes.

ascending: growing erect after an oblique or semi-horizontal beginning.

asexual: not forming part of a cycle which involves fertilisation and meiosis.

asperulate: slightly rough to the touch.

attenuate: tapering gradually.

auricle: an ear-shaped appendage at the base of a leaf, leaflet or corolla lobe. adj. auriculate.

autapomorphic: of a character, derived and unique to a given taxon or monophyletic group. cf. apomorphic, synapomorphic.

autochthonous: of the inhabitants of a region, original; earliest known; (applied to an element of the Australian flora rich in endemics and believed to have been evolving in Australia for a long period of time).

autotrophic: independent of other organisms in respect of organic nutrition; able to fix carbon dioxide, by photosynthesis, to form carbohydrates. cf. epiphyte, parasite, saprophyte.

auxotelic: applied to inflorescences, parts of inflorescences or to axes that do not end in a flower, and in which growth continues beyond the flowering region, cf. anauxotelic.

awn: a bristle-like appendage, e.g. on the tip or back of the lemma of a grass floret.

axil: the angle between a leaf or bract and the axis bearing it. adj. axillary.

axile: on an axis; of a placenta, on the central axis of the ovary.

axis: a stem, (commonly used for the main stem of a whole plant or of an inflorescence).

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Last updated on 13 May 1999.

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