taken place by means of Natural Selection, or, in other 
words, by the survival of favourable variations which arise 
in connection with sexual reproduction. 
The displacement ,of one species by another may be 
due to independent action on the part of each to adapt 
itself to new conditions in which it is placed. In that 
case, one fails and the other succeeds. Mr. Wallace refers 
to several cases in which the attempt to naturalise a new 
species has met with no success. 
“Attempts to naturalise suitable plants usually fail, for A. de 
Candolle states that several botanists of Paris, Geneva, and especially 
of Montpellier, have sown the seeds of many hundreds of species 
of hardy exotic plants in what appeared to be the most favourable 
situations, but that, in hardly a single case, has any one of them 
become naturalised. Even a plant like the potato—so widely culti 
vated, so hardy, and so well adapted to spread by means of its many 
eyed tubers—has not established itself in a wild state in any part 
of Europe. It would be thought that Australian plants would easily 
run wild in New Zealand ; but Sir Joseph Hooker informs us that 
the late Mr. Bidwell habitually scattered Australian seeds during 
his extensive travels in New Zealand, yet only two or three Australian 
plants appear to have established themselves in that country, and 
these only in cultivated or newly moved soil.”—(Wallace. Dar 
winism. pp. 15-6.) 
All these instances illustrate the point that some plants 
are unable to adapt themselves to the new conditions 
in which they are placed, especially if they be suddenly 
transplanted to a new sphere. In other cases plants would 
seem to have a power of adaptation which enables them to 
overcome the disabilities of their new habitat. We may 
thus account for the survival of certain plants in the 
pampas of the southern part of South America. Mr. 
Edward Clark tells us that the country is characterised 
by the absence of rivers and water storage, by the 
periodical occurrence of droughts or siccos in the summer 
months ; and that the open plain is overrun by number 
less wild rodents, the original tenants of the pampas,