Glossary of Botanical Terms - O

O

ob-

inversely; usually same shape as suffix but attached by the narrower end, for example obcordate, oblanceolate, obovate.

obconic

of a fruit, hypanthium, pistil or calyx structure; an inverted cone shape.

obcordate

of a leaf blade, broad and notched at the tip; heart shaped but attached at the pointed end.

oblanceolate

a 2-dimensional shape, lanceolate but broadest in the upper third; cf. lanceolate.

obligate

of parasites, unable to survive without the host; compare faculative.

oblique

slanting; of a leaf, larger on one side of the midrib than the other, in other words asymmetrical.

oblong

length a few times greater than width, with sides almost parallel and ends rounded.

obovate

of a leaf, a 2-dimensional shape of which the length is about 1.5 times the width, and widest above the centre.

obtuse

blunt or rounded at the tip or apex; converging edges making an angle of more than 90°; compare acute. See Leaf shape.

Oceania

the islands of the Pacific (sometimes including Australia).

ocrea (ochrea)

a sheath, formed from two stipules, encircling the node in Polygonaceae.

odd-pinnate

(imparipinnate) having an odd number of leaflets in a compound leaf.

Old World

the world known before the discovery of America; essentially Europe and Asia.

olim

formerly, e.g., "olim B", formerly in the Berlin herbarium (Herbarium Berolinense).

ontogeny

the sequence of developmental stages through which an organism passes.

operculum (calyptra)

a lid or cover that becomes detached at maturity, e.g. in Eucalyptus, a cap covering the bud and formed by the fusion or cohesion of perianth parts.

opposite

(as adjective) leaves or flowers borne at the same level but on opposite sides of the axis; or (as verb) when something occurs on the same radius as something else, for example anthers opposite sepals; compare alternate.

opera utique oppressa (plural), and opus utique oppressum (singular)

listed after the botanical name of a plant, or the name of a publication, this indicates that a publication is listed in the International Code of Nomenclature for algae, fungi, and plants as a suppressed work. Botanical names of the specified rank in the publication are considered not validly published (article 32.9).

orbicular

flat and more or less circular.

order

a group of one or more families sharing common features, ancestry, or both.

ortet

the original single parent plant from which a clone ultimately derives.

orthotropous

when an ovule is erect, with the micropyle directed away from the placenta; atropous; cf. amphitropous, anatropous, campylotropous.

oval

see elliptical.

ovary

the basal portion of a carpel or group of fused carpels, enclosing the ovule(s).

ovate

shaped like a section through the long-axis of an egg and attached by the wider end.

ovoid

egg-shaped, with wider portion at base; 3-dimensional object, ovate in all sections through long-axis.

ovule

loosely, the seed before fertilization; a structure in a seed plant within which one or more megaspores are formed (after fertilization it develops into a seed).