Opposite, said of leaves and branches when on opposite sides of the stem from each other (i. e. in pairs), [29], [68]. Stamens are opposite the petals, &c., when they stand before them.
Oppositifolius, situated opposite a leaf.
Orbicular, Orbiculate, circular in outline, or nearly so, [52].
Order, group below class, [178]. Ordinal names, [180].
Organ, any member of the plant, as a leaf, a stamen, &c.
Organography, study of organs, [9]. Organogenesis, that of the development of organs.
Orgyalis, of the height of a man.
Orthos, Greek for straight; thus, Orthocarpous, with straight fruit; Orthostichous, straight-ranked.
Orthotropous (ovule or seed), [111].
Osseous, of a bony texture.