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.

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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.

pandurate: fiddle-shaped.

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).

pectinate: comb-like.

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.

pellucid: transparent.

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.

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Last updated on 13 May 1999.

Australian Biological Resources Study