Australian Flowering Plants. 187 



action of isolation from the ancient home, in producing great 

 changes in the nature of the evolution of new genera, sub- 

 genera, and species. Two examples may be taken, namely, 

 Hawaii and St. Helena. From the geological evidence, neither 

 of these appears to have been in direct connection with the 

 great land blocks, such as North America in the case of Hawaii, 

 and of West Africa in the case of St. Helena. Nevertheless 

 their endemic flora is so rich and varied as to suggest the 

 cumulative action of time and of evolution, under isolation, in 

 producing numerous endemic species, if not genera, from the 

 waifs brought to them by the sea, by birds, or by man since 

 their existence as islands. 



In this connection attention may be drawn to the magnificent 

 work of Wallace, 9 Guppy, 10 and Hemsley, 11 on Insular Floras. 

 The study of these volumes is of the utmost service in clearing 

 the way for a proper discussion of the population of islands 

 by various agencies. 



Man. The importance of this agent, in the transport of 

 plants from land to land across the sea, appears to have been 

 almost always underestimated. Anyone who has lived with 

 native races of men must have noted their belief in the necessity 

 of certain plants to their well-being, either as articles of food 

 or as medicines. Man has had a long history on the globe, 

 and in his many wanderings, both in the primitive and civi- 

 lized state, he must have been the means, consciously or uncon- 

 sciously, of carrying many plants from the northern hemisphere 

 to the southern or from the east to the west and so on. Certain 

 of the Compositse, Cruciferse, Labiatse, Umbelliferae, Caryophyl- 

 lacese, Rosacea?, and other families, may be conceived as having 

 been transported in this way, for example, Taraxacum officinale. 



(2) The Distribution of Mammals. 



Inasmuch as it is necessary to apply the testimony of inde- 

 pendent witnesses, whenever possible, as to supposed land con- ■ 

 nections during particular periods of the earth's history, it 

 would, in the case of the angiospermous distribution, be advis- 

 able, if possible, to apply the testimony of the animals. 



The distribution of reptiles, birds, worms, and invertebrates 

 generally does not concern us, necessarily, in the distribution 

 of the flowering plants, inasmuch as they had their origin long 

 before that of the angiosperms, and they, therefore, may have 



"Island Life, 1892. 



10 A Naturalist in the Pacific, Plant-Dispersal, vol. ii, 1906. 



11 The Voyage of the Challenger, Botany, vol. i, Introduction. 



Am. Jour. Sci. — Fourth Series, Vol. XLII, No. 249. — September, 1916. 

 13 



