260 A NATURALIST IN THE PACIFIC CHAP. 



to go behind the mere capacities for dispersal and to appeal to the 

 general laws of distribution in so far as our facts enable us to 

 interpret them. 



We have seen that the two principal components of the early 

 Pacific flora, the Compositse and the Lobeliaceae, have American 

 affinities. The plants of the later ages are mainly Old World in 

 their connections. Though containing often endemic species in 

 the various groups, the genera occur also outside each group. 

 The stream of migration that came from America during the early 

 age of the Compositae and the Lobeliaceae, when the islands 

 of the Western Pacific were more or less submerged, was during 

 the later ages (after these islands had re-emerged) suspended 

 or diverted, giving place to a stream that brought plants in 

 numbers from tropical Asia, Malaya, and Australia. The general 

 dispersion of the Compositae and Lobeliaceae took place during 

 the Tertiary submergence of the islands of the Western Pacific, 

 including the island-groups of Fiji, Samoa, and Tonga. The 

 migration from the west, mainly Indo-Malayan in character, 

 occurred after the re-emergence of those archipelagoes. Thus we 

 get to understand how genera like those of the early Lobeliaceae 

 and Cyrtandra, which possess, as regards the minute size of their 

 seeds, closely similar capacities for dispersal, have such different 

 distributions, the first confined to Hawaii and Tahiti and American 

 in their affinities, the second widely spread over the Pacific with its 

 home in Malaya. 



We have yet to inquire whether this suspension of the means 

 of transport in the later ages of the Pacific Lobeliacese is confined 

 to the tropics or whether it extends to the colder latitudes in the 

 southern hemisphere. The indications of the Lobeliaceae of the 

 " antarctic flora " go to establish that the dispersal of the order is 

 still, or was very recently, in operation in these high latitudes. It 

 is well illustrated, among other plants, by Lobelia anceps, which is 

 found in extra-tropical South America, Australia and New Zealand, 

 and South Africa. This, indeed, recalls Bentham's view concerning 

 the Compositae, that whilst communication was broken off in the 

 tropics, it was kept up in higher latitudes. 



Here ends, therefore, our consideration of the Tree-Lobelias of 

 the Pacific islands ; but as it is not quite complete without a dis- 

 cussion of the remaining endemic genera of other orders than 

 the Compositae and Lobeliaceae which also belong to the same 

 early age of the Pacific floras, I will proceed at once to their 

 consideration. 



