Glossary: O

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OBL

Obligate Wetland: plant occurs almost always in wetlands (probability > 99%).

oblanceolate

Widest above the middle point between the point of attachment and the apex, and tapering at both ends; narrower than obovate but wider than linear (compare lanceolate).

oblique

Emerging at an angle other than perpendicular or parallel.

oblong

Shaped similar to a rectangle that is longer than wide and with rounded ends.

oboloid

Three-dimensional equivalent of oblong.

obovate

Roughly oval, widest above the point of attachment and the apex (compare ovate), and broadly tapering to each end; wider than oblanceolate.

obtriangular

Any triangular shape with the broad end toward the apex.

obtuse

Bluntly pointed, with the margins forming an angle of greater than 90°.

ocrea

A tubular stipule where the leaf base sheaths the stem (in species of the buckwheat family, Polygonaceae); alternate spelling: "ochrea".

opposite

Positioned directly across from one another; referring to the arrangement of a node that bears 2 similar organs (compare with basal, alternate, whorled).

orbicular

Circular in outline.

organ

A plant structure that performs a metabolic, structural, or reproductive function, such as a leaf, stem or flower.

orifice

Opening into a cavity.

ornamented

With elaborate patterns or textures.

ovary

The expanded basal portion of a carpel that bears the immature seed.

ovate

Egg-shaped, widest below the middle and broadly tapering to each end; wider than lanceolate.

ovoid

The 3-dimensional equivalent of ovate; shaped like an egg widest below the middle.

ovule

An immature seed.