obconical: cone-shaped but attached at the narrower end.
obcordate: of a leaf blade, broad and notched at the tip; heart-shaped but attached at the pointed end.
oblanceolate: similar in shape to lanceolate but attached at the narrower end.
obligate: of parasites, unable to survive without the host. cf. facultative.
oblique: of a leaf or leaflet, larger on one side of the midrib than on the other, i.e. asymmetrical.
obloid: a three-dimensional shape, with short, parallel sides and rounded ends, as if composed of two hemispheres linked together by a short cylinder.
oblong: a two-dimensional shape, having the length greater than the width but not many times greater, and the sides parallel.
obovate: similar in shape to ovate but attached at the narrower end.
obovoid: similar in shape to ovate, but attached at the narrower end.
obsolescent: non-functional but not reduced to a rudiment.
obsolete: reduced to a rudiment, or completely lacking. cf. rudimentary, vestigial.
obtuse: blunt or rounded at the apex, the converging edges separated by an angle greater than 90 degrees.
ochrea: a sheath, formed from two stipules, encircling the node in Polygonaceae.
ontogeny: the development of a single organism, i.e. the sequence of stages through which it passes during its lifetime.
operculum: in a flower, a cap formed by fusion or cohesion of perianth parts and covering the stamens and carpels in the bud, becoming detached at maturity by abscission; especially in Eucalyptus, see calyptra.
opposite: of leaves or other lateral organs, borne at the same level but on opposite sides of the stem; of floral parts, on the same radius. cf. alternate.
orbicular: circular or nearly so.
order: a taxonomic grouping of families believed to be closely related (sometimes a single family with no apparent close relatives); the major taxonomic rank between family and class.
orthotropous: of an ovule, erect so that the micropyle points away from the placenta.
ostiole: an opening or pore, e.g. at the apex of a fig.
ovary: the basal portion of a carpel or group of fused carpels, enclosing the ovule(s).
ovate: a two dimensional shape, like a section through the long axis of an egg, and attached by the wider end.
ovoid: egg-shaped (in three dimensions).
ovulate: with ovules.
ovule: a structure in a seed plant within which one or more megaspores are formed and which develops into a seed after fertilisation.
ovuliferous: bearing ovules, e.g. applied to scales in a megasporangiate cone in gymnosperms.
ovulode: sterile structures on the placenta.
Back to Glossary Index
palea: in a grass floret, the upper one of the two bracts enclosing a flower.
palmate: of a leaf, divided into several leaflets which arise at the same point.
palmatifid: of a leaf, deeply (but not completely) divided into several lobes which arise (almost) at the same level. cf. pinnatifid.
palmatinerved: of leaves, palmately nerved, i.e. with the (main) nerves radiating from one basal point.
palmatisect: a condition intermediate between palmate and palmatifid, with the green tissue of the lamina completely divided into several segments, but the segments not fully separated at the base.
palynology: the scientific study of pollen.
panicle: a compound raceme; an indeterminate inflorescence in which the flowers are borne on branches of the main axis or on further branches of these.
paniculate: indeterminate and much branched.
pantoporate: of a pollen grain, with rounded apertures all over the surface.
papilla: a small, elongated protuberance on the surface of an organ, usually an extension of one epidermal cell. adj. papillose.
pappus: a tuft of hairs on a fruit; in Asteraceae, a tuft (or ring) of hairs or scales borne above the ovary and outside the corolla and possibly representing the calyx.
parapatric: of distributions of two taxa or populations, having non-overlapping but contiguous ranges. cf. allopatric, sympatric.
paraphyletic: a group of taxa derived from a single ancestral taxon, but which does not contain all the descendants of the most recent common ancestor.
paraphyses: sterile filaments in the fruiting bodies of non-vascular plants.
parasite: an organism living on or in a different organism and deriving nourishment from it. cf. autotrophic, epiphyte, saprophyte.
paratype: a specimen or illustration, other than the holotype, isotype or one of the syntypes, that was cited with the original publication of a name. cf. type.
parenchyma: plant tissue consisting of mature, living cells that are relatively unspecialised in function.
parietal: attached to the margins of a structure; of placentation, having the ovules attached to placentas on the wall of the ovary.
paripinnate: having an even number of pinnae by virtue of having a pair in the terminal position. cf. imparipinnate.
-partite: divided, almost to the base, into segments (commonly applied to a style or leaf).
pedate: of a palmate or palmately-lobed leaf, having the lateral segments divided again.
pedicel: the stalk of a flower. adj. pedicellate.
peduncle: the stalk of an inflorescence; in ferns, the stalk of a sporocarp. adj. pedunculate.
peloric: actinomorphic, of a flower which, from its taxonomic context, would be expected to be zygomorphic, e.g. in Orchidaceae. cf. actinomorphic, zygomorphic.
peltate: of a leaf, having the stalk attached to the lower surface of the blade, not to the margin (also applied, in the same sense, to other stalked structures).
pendulous: drooping; of ovules, attached at the top of the ovary and hanging downwards from an apical placenta.
penicillate: pencil-shaped; tufted like an artist's brush.
penninerved (= penniveined): having conspicuous lateral veins divergent from the midrib and lying approximately parallel to each other.
pentamerous: of a flower, having five segments in each perianth whorl, and usually five in each whorl of stamens also.
pepo: a fruit with firm skin, pulpy interior, many seeds and a single locule; species epithet for a group of cucurbits including squash, zucchini and some pumpkins and gourds.
perennate: maintain a dormant, vegetative state throughout non-growing seasons.
perennial: a plant whose life span extends over more than two growing seasons. cf. annual, biennial.
perfoliate: of a sessile leaf or bract, having its base completely wrapped around the stem.
perianth: the calyx and corolla of a flower, especially where the two are similar.
pericarp: the wall of a fruit, developed from the ovary wall.
perigynous: of perianth segments and stamens, arising from a cup or tube (hypanthium) that is free from the ovary but extending above its base. cf. epigynous, hypogynous.
perisperm: nutritive tissue in an angiospermous seed, formed from the nucellus. cf. endosperm.
persistent: remaining attached to the plant beyond the expected time of falling, e.g. of sepals not falling after flowering.
petal: a member of the inner whorl of non-fertile parts surrounding the fertile organs of a flower, usually soft and coloured conspicuously.
petaloid: like a petal; soft in texture and coloured conspicuously.
petiole: the stalk of a leaf.
petiolule: the stalk of a leaflet.
phalange: a bundle comprising several structures fused together; a group of connate carpels, e.g. in Pandanaceae.
phanerogam: (literally) a plant with conspicuous reproductive parts; a plant reproducing by seeds. cf. cryptogam.
phenotype: the physical characteristics of an organism; the outward expression of characteristics conferred on an organism by its genotype. cf. genotype.
phloem: the tissue in the conducting system of a plant through which metabolites (products of chemical reactions in the plant) are transported.
phyllichnium: in Casuarinaceae, the ridge of a branchlet segment; pl. phyllichnia.
phylloclade: a very leaf-like, photosynthetic stem of a plant whose true leaves are much reduced. cf. cladophyll.
phyllode: a leaf whose blade is much reduced or absent, and whose petiole and rachis have assumed the functions of the whole leaf. cf. cladode.
phyllotaxy: the arrangement of leaves on a stem (when spiral, often expressed quantitatively as the fraction of the circumference of the stem that separates two successive leaves).
phylogeny: the evolutionary development of a plant group, i.e. its derivation from its ancestors and the relationship among its members. adj. phylogenetic.
phylum: an alternate name for division, the major taxonomic rank below Kingdom.
pilose: hairy, the hairs soft and clearly separated but not sparse.
pinna: a primary segment of the blade of a compound leaf. pl. pinnae.
pinnate: divided into pinnae; once-compound. cf. bipinnate, tripinnate.
pinnatifid: cut deeply (but not to midrib) into lobes that are spaced out along the axis (of the leaf). cf. palmatifid, ternatifid.
pinnatipartite: of leaves, pinnatifid, where the lobes pass beyond the middle (or are within the middle third) and the parenchyma is not interrupted.
pinnatisect: dissected down to the midrib but having the segments confluent with it.
pinnule: a leaflet of a bipinnate leaf.
pistil: a free carpel or a group of fused carpels.
pistillode: a sterile pistil, often rudimentary.
pith: the central region of a stem, inside the vascular cylinder.
placenta: a region, within an ovary, to which ovules are attached.
placentation: the arrangement of placentas, and hence of ovules, within an ovary.
plesiomorphic: of a character, ancestral or primitive. cf. apomorphic.
plicate: folded back and forth longitudinally like a fan.
plietesial: monocarpic but living for several years before flowering.
plumose: like a feather; with fine hairs branching from a central axis.
plumule: the portion of an embryo that gives rise to the shoot system (as distinct from the root system) of a plant. cf. radicle.
pneumatophore: an air-vessel; an organ containing aerenchyma; in particular, a root of a mangrove plant, growing above the substratum.
pod: a leguminous fruit.
pollen: the microspores of seed plants; the powdery mass of microspores shed from anthers.
pollen-grain: a microspore of a seed plant, or the partially developed gametophyte formed from it.
pollen presenter: of many Proteaceae, a structural modification, usually a swelling, of the style around or below the stigma which enables pollen, shed in the bud, to be retained.
pollen-sac: a cavity, in an anther, in which pollen is formed.
pollination: the transfer of pollen from the male organ, where it is formed, to the receptive region of a female organ, e.g. from anther to stigma.
pollinarium: the complex structure found in flowers of Asclepiadaceae and Orchidaceae where the pollen masses of the two adjacent anther-lobes (thecae) are united for dispersal as a unit. The pollinarium consists of two pollinia, attached by caudicles to a central corpusculum. pl. pollinaria.
pollinium: pollen-mass, the aggregation of all the pollen of one anther-lobe (theca) into one unit for transfer in pollination. pl. pollinia.
polygamodioecious: with bisexual and male flowers on some plants, and bisexual and female flowers on others.
polygamomonoecious: with bisexual flowers and unisexual flowers of both sexes on the same plant.
polygamous: having bisexual and unisexual flowers on the same or different plants.
polymorphic: having more than two distinct morphological variants.
polypetalous: with free petals. cf. sympetalous.
polyphyletic: composed of members that originated, independently, from more than one evolutionary line. cf. monophyletic.
polyploid: having more than two of the basic sets of chromosomes in the nucleus. cf. diploid, haploid.
polytypic: containing more than one taxon of the next lower rank, e.g. applied to a family containing more than one genus. cf. monotypic.
pome: a fleshy (false) fruit, formed from an inferior ovary, in which the receptacle or hypanthium has enlarged to enclose the true fruit.
porate: of a pollen grain, with rounded apertures (called pores) only. cf. colporate, colpate.
poricidal: of anthers or capsules, opening by pores.
porrect: of a trichome, having branches spreading more or less horizontally from the top of an erect stalk.
posterior: of floral organs, on the side of the flower nearest to the axis. cf. anterior.
praemorse: appearing bitten off at the end.
prickle: a hard, pointed outgrowth from the surface of a plant, involving several layers of cells but not containing a vein.
process: as part of a plant, a projecting outgrowth or appendage.
procumbent: trailing or spreading along the ground but not rooting at the nodes.
proliferous: able to reproduce vegetatively from the shoot system, e.g. by stems rooting at the nodes (as in Conostylis); producing plantlets on leaves or fronds (Pteris) or in the inflorescence (Isolepis).
propagule: a structure with the capacity to give rise to a new plant, e.g. a seed, a spore, part of the vegetative body capable of independent growth if detached from the parent.
prophyll: a leaf formed at the base of a shoot, usually smaller than those formed subsequently.
prostrate: lying flat on the ground.
protandrous: having the male sex organs maturing before the female; of a flower, shedding the pollen before the stigma is receptive. cf. protogynous.
prothallus: a gametophyte body, especially in bryophytes, ferns and related plants.
protogynous: having the female sex organs maturing before the male; of a flower, shedding the pollen after the stigma has ceased to be receptive. cf. protandrous.
proximal: near to the point of origin or attachment. cf. distal.
pruinose: having a whitish, waxy, powdery bloom on the surface.
pseudanthium: a compact inflorescence of several to many small flowers which simulates a single flower.
pseudo-: false; apparent but not genuine.
ptyxis: pattern of folding and rolling shown during leaf development.
puberulous: covered with minute, soft, erect hairs.
pubescent: covered with short, soft, erect hairs.
pulverulent: appearing as though dusted over with powder.
pulvinate: cushion- or pad-shaped, resembling a pulvinus.
pulvinus: a swelling at the base of the stalk of a leaf or leaflet, often glandular or responsive to touch.
punctate: marked with dots.
puncticulate: minutely dotted.
pungent: ending in a stiff, sharp point; having an acrid taste or smell.
pustulate: covered with small pustule- or blister-like elevations.
pyrene: the 'stone' (endocarp plus seed) of a succulent fruit. cf. berry, drupe.
Back to Glossary Index
This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from Australian Biological Resources Study. Requests and inquiries concerning reproduction and rights should be addressed in the first instance to the Executive Editor - Flora. These pages may not be displayed on, or downloaded to, any other server without the express permission of ABRS.
Last updated on 13 May 1999.