1890.] Certain Peculiarities in the Flora. 219 
of life so far away is small. It may be well to look about in 
order to discover, if possible, other causes nearer the locality for 
an explanation of this destruction of continental species and the 
survival of older characteristic genera on the neighboring islands. 
I think there are other and possibly more effective causes which 
have had a profound influence in Southern California in this direc- 
tion. 
When hardy ® species were driven south by glacial cold, they 
were certainly more fitted to survive in the cold climate than 
the denizens of a warmer climate which they encountered, simply 
because the climate was colder. But when the glacial cold was 
mitigated the animals and plants of warmer climates were more 
fitted to survive, and in a struggle for existence would be stronger 
than the “ hardy ” or those fitted for glacial cold or comparatively 
low temperatures. Then their influence would be greatest. As 
the character of the insular flora was less affected than the main 
land by the hardy animals, we may also suppose it to be less 
affected than the main land by the return of the warm climate 
animals at the restoration of a more genial climate. Conse- 
quently, not only glacial cold but subsequent milder temperature 
have acted in unequal degrees upon the inhabitants of islands and 
main land. If there was a return of conditions of climate similar 
to that of the Pliocene, like plants to those of the insular flora 
might be expected to reappear. But anew influence has made 
inself powerful in modifying environment. The main land has 
become more desiccated than it formerly was. From the nature 
of their position the islands are not as profoundly affected by this 
influence as the continent. Like a huge Briarzeus desiccation has 
spread itself over the south-west, so that, while its influence is 
exerted on the insular flora, it is not in as marked a manner as 
on the main land. So potent is this influence that it cannot be 
lost sight of, and is even as important as glacial cold. We must 
not forget, also, the profound influence on climate, and, conse- 
quently, on the facies of organic life, which the out-pouring of 
3 More suited to live under conditions of glacial cold. “ Hardy” genera may, under 
condition of heat or dryness, become feeble. The word as here rganisms 
which are more fitted to live in cold climates. 
