MO UNTAIN-FL OR AS 
149 
back in Tertiary times ; these have been able to survive on 
the islands with little or no modification, whilst they have 
disappeared from the continental areas. The number of 
species in island-floras is usually small and the struggle for 
existence among them probably less keen and complex, and 
thus not merely have old forms been enabled to survive, but 
the adaptation of the various plants to their environment is 
not very perfect. This is shown by the way in which 
introduced species from large continental areas spread over 
islands at the expense of the indigenous flora. A large 
number of European plants are naturalised in most oceanic 
islands, and many of the native forms have become rare or 
extinct, e.g. in St Helena and even in such large islands as 
Australia and New Zealand. 
The floras of oceanic islands generally show a large 
proportionate representation of orders and genera. Woody 
or subarboreal habit is common ; also the possession of 
small, narrow leaves. Flowers are commonly small and 
inconspicuous (see Pringlea). 
Mountain- Floras 1 . Mountain regions may be com- 
pared with islands, the higher parts differing so much in 
climate &c. from the lower parts and the lowlands from 
which they rise as to form isolated regions in which new 
forms may be evolved. With few exceptions all the higher 
mountain ranges are characterised by the possession of 
numerous endemic species and genera. The mountains of 
Britain, Scandinavia, Kamtschatka, &c. do not show this 
character. Their flora resembles that of the arctic regions, 
having been derived from it during the glacial period. In 
the Pyrenees, Alps, &c., though there are many arctic forms, 
there are many endemic genera and species. 
We have already pointed out that mountain chains act 
as highways of migration (as do railway-embankments on a 
small scale). The universally American character of the 
floras of the different parts of America from north to south 
is probably in part to be ascribed to the long chain of the 
Rocky Mountains and the Andes, which has formed a 
1 Engler, Die Pfianzenformationen..,d . Alpenkette , Notizbl. k. Bot. 
Gtns., Berlin, Appendix vn, 1901 ; Jaccard, Gesetze d. PJlanzen- 
vertheilung in d. alpiner Region , Flora, '90, p. 349 ; and see Alpine 
Plants, below. 
