Polanisia, i, 378.
Potamogeton Claytoni, xlv, 38.
— pulcher, xlv, 38.
Potentilla supina, xiv, 114.
Prenanthes aphylla, v, 299.
Primula farinosa, iv, 59.
Prinos coriaceus, v, 293.
Prosartes maculata, xlvii, 201.
Protococcus kermesinus, analogies of, with the red particles of the blood, xxxvi, 206.
Prunus pennsylvanica, xiv, 112.