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 ovate but wider than linear; lance-shaped (compare lanceolate).
Obligate Wetland
Almost always occurs in wetlands in standing water or seasonally saturated soils.
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 lanceolate.
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°.
Ochlerotatus pullatus Ochlerotatus pullatus
Mosquito, photo ©David Inouye.
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 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.
Osmia proxima Osmia proxima
Mason Bee, photo courtesy Packer Laboratory, York University with assistance of Robert and Cecily Bradshaw and Canadensys.
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.
Oxydia vesulia Oxydia vesulia
Spurge Spanworm Moth, photo ©Jim Vargo, North American Moth Photographers Group.