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Australian Biological Resources Study

Flora of Australia

Compiled by A.McCusker


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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. > image <

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. > image <

obovate: similar in shape to ovate but attached at the narrower end. > image <

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. > image <

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. > image | image <

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. > image <

orbicular: circular or nearly so. > image <

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). > image <

ovate: a two dimensional shape, like a section through the long axis of an egg, and attached by the wider end. > image <

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. > image <

ovuliferous: bearing ovules, e.g. applied to scales in a megasporangiate cone in gymnosperms.

ovulode: sterile structures on the placenta.

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