Oakesia Conradii, xlv, 215.
Œnothera sinuata, xi, 180.
Olea americana, northern limit of, H. B. Croom, xxvi, 315.
Oligostachyum, iv, 58.
Orchis tribe, synonymy of some species of, A. Gray, xxxviii, 306.
Orchis spectabilis, monstrous flower of, J. W. Bailey, xxxv, 117.f
Oxyria reniformis, xlv, 29.
Panicum longisetum, iv, 58.
Passiflora Warei, v, 297.