on geology of Spitzbergen, [188]
North America, glacial phenomena in, [116]
interglacial warm periods in, [121]
condition of, in Tertiary period, [194]
Northern genera of plants in S. temperate America, [521]
hemisphere, absence of southern plants from, [527]
flora, hardiness of, [528]
O.
Ocean-currents as carriers of plants, [81]
as affecting interglacial periods, [152]