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Glossary: O

Obligate Wetland: plant occurs almost always in wetlands (probability > 99%).
oblanceolate 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 oblique
Emerging at an angle other than perpendicular or parallel.
oblong oblong
Shaped similar to a rectangle that is longer than wide and with rounded ends.
Three-dimensional equivalent of oblong.
obovate obovate
Roughly oval, widest above the point of attachment and the apex (compare ovate), and broadly tapering to each end; wider than oblanceolate.
obtriangular obtriangular
Any triangular shape with the broad end toward the apex.
obtuse obtuse
Bluntly pointed, with the margins forming an angle of greater than 90°.
ocrea ocrea
A tubular stipule where the leaf base sheaths the stem (in species of the buckwheat family, Polygonaceae); alternate spelling: "ochrea".
opposite 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 orbicular
Circular in outline.
A plant structure that performs a metabolic, structural, or reproductive function, such as a leaf, stem or flower.
orifice orifice
Opening into a cavity.
ornamented ornamented
With elaborate patterns or textures.
ovary ovary
The expanded basal portion of a carpel that bears the immature seed.
ovate ovate
Egg-shaped, widest below the middle and broadly tapering to each end; wider than lanceolate.
ovoid ovoid
The 3-dimensional equivalent of ovate; shaped like an egg widest below the middle.
ovule ovule
An immature seed.