The archipelago is the most completely isolated region of equal size in the world, with the highest proportion of endemic spp. 163 indigenous monocots and 889 indigenous dicots have been described; of the former, about 73% are endemic; of the latter, about 93%. The islands are entirely volcanic in their formation, but there is great variation of temp. and precipitation, due to the range of elevation from sea-level to over 13,000 ft. The lee shores of the higher islands are arid, while precipitation of 400-500 in. has been recorded in some windward stations. The principal botanical formations are: (1) Strand flora; (2) lowland; (3) lower forest; (4) middle forest; (5) mountain bogs; and (6) upper forest. The lowlands, and much of the lower forest, are under cultivation and a considerable number of exotics have become naturalized. A very large percentage of the spp. have their nearest relatives in the southern Pacific countries[long dash]New Zealand, Australia, and the Malayan regions[long dash]while the American elements are much less evident. About 50 extra-American genera are common to Hawaii and the South Pacific countries, while the peculiarly Hawaiian-American genera are scarcely 6. As examples of Old World genera may be cited Pandanus, Gardenia, Pittosporum, Santalum, Cyathodes, Coprosma, etc. The relationships between Hawaii and New Zealand are especially interesting. The American element in the Hawaiian flora is evidently derived from the Pacific Coast of N. Amer., e.g., Fragaria chilense, Sisyrynchium, and a number of Compositae clearly related to Californian genera. The Lobeliaceae has about 100 spp., the majority of which belong to 5 endemic genera. The absence of conifers and the genus Ficus and the Araceae is noteworthy. There are also only 4 orchids, out of the 17,000 known spp. The existing fauna and flora are best explained by the assumption that the islands were once more or less directly joined to the lands of the South Pacific area, with whose plant and animal life the organisms of the islands are evidently related. The transport of most of these to Hawaii from the remote regions to the south, over the ocean, is quite inconceivable. On the other hand, the introduction of the American types is quite comprehensible, as there are regular bird migrants between America and the islands, and the N. E. trade winds and ocean currents may also have served as means of transport.