119 
Chap. VIII.— B.S.J STRUGGLE FOR EXISTENCE. 
country, it is ever at work; but it becomes much more 
intense when species from abroad appear on the field, 
or, at all events, from our being able to recognize at a 
glance the opposing elements, we are in a better posi¬ 
tion to watch the struggle and its issue. A prominent 
example of such a battlefield, if so martial a term be 
admissible, is the island of St. Helena, where the na¬ 
tive vegetation is at present almost entirely superseded 
by a foreign one, some of the singular indigenous tree- 
Compositce now existing in only one or two old spe¬ 
cimens. In many parts of the Cape of Good Hope 
an equally great change is noted, and many species 
are in danger of becoming altogether extinct. I 
remember the venerable explorers, Ecklon and Zeyher, 
taking me to the foot of Table Mountain to see a few 
silver-trees (.Leucadendron argenteum ), which, they 
assured me, were the only specimens in South Africa. 
Dr. Hooker, in his suggestive papers ‘ On the Struggle 
of Existence amongst Plants,’ has well pointed out 
the rapid spread of European species in Hew Zealand, 
and the displacement of the indigenous. The altera¬ 
tions wrought in Europe by the naturalization of 
foreign plants are familiar to us all; and Central Ame¬ 
rica and many other parts of the inhabited globe 
might be pointed out where the same phenomenon is 
observable. Foreign plants deport themselves towards 
the indigenous as an invading army does towards the 
inhabitants of a hostile country. Before the bulk of 
the army advances, outposts make their appearance, 
consisting of the most daring and hardy fellows. In 
the vegetable kingdom the office of outposts is per- 
