Œninghen, Miocene flora of, [183]
Œnothera odorata, on a railway bank, [514]
Oliver, Professor, on peculiar Bermudan plants, [272]
Operculata, scarcity of, in the Sandwich Islands, [317]
Ophrys apifera, temporary appearance of, [514]
Orchideæ, species have restricted ranges, [505]
Orchids, abundance of, in Bourbon and Mauritius, [446]
why almost universal in the tropics, [446]
Orders, distribution of, [30]
Organic change dependent on change of conditions, [225], [228]