960 PATAGONIAN EXPEDITIONS: BOTANY. 



favors the supposition that if ever a connection existed, it must have 

 been of the nature of stepping-stones rather than of a bridge. There are 

 also indications of some passage between South Africa and South America, 

 but as to the nature and limitations of this we are ignorant. In some 

 instances at least the connection seems to have been via the highlands of 

 Eastern Africa, and the circuitous route by the Asiatic highlands and 

 Bering Strait. 



As a general rule, the plants appear to us to be a match for the animals 

 in their power to survive adverse conditions, probably through their 

 ability to revive after long periods of dormancy. They can passively 

 extend their spheres, and on reaching new localities they may or may not 

 experience a conversion into new varieties or species. If the Ice-age 

 drove temperate plants southwards in North America, we may conclude 

 that a return of milder seasons would not send them all back again 

 towards the poles ; but some would be allured by mountain ranges, rich 

 in moisture and with cool air, to push their way farther south, ultimately 

 reaching Southern Chili, and a few of them even leaving vestiges on the 

 mountains of Central America or Peru. Thus the very same species 

 sometimes occurs in Alaska and at Magellan Straits, as if the northern 

 plants had made raids southwards, probably on more than one occasion, 

 and had never failed to leave some of their party behind as permanent 

 settlers. 



