Obconically. Inversely conical, having the attachment at the apex.
Obcordate. Inverted heart-shaped.
Oblanceolate. Lanceolate with the broadest part toward the apex.
Oblique. Unequal-sided or slanting.
Oblong. Considerably longer than broad and with nearly parallel sides.
Obovate. Inverted ovate.
Obovoid. Having the form of an inverted egg.
Obsolete. Not evident; rudimentary.
Obtuse. Blunt or rounded at the end.
Ocrea. A leggin-shaped or tubular stipule.