sunny parterres beckon to the spying trees, prom¬ 
ising centuries of occupation—if they can stand 
the climate. 
The rising heat rolling in waves from the south, 
nearer and nearer, urges on the lagging columns, 
adding the necessity of avoiding death to the 
attraction of better homes. 
But the universal return of plants from the south, 
was prosecuted under vastly different, more de¬ 
structive conditions than those of the northern 
flight. The plants on the return trip were attracted 
northward along the cool plains, and also, some of 
them upward on the mountainsides, for it is the 
same thing in effect, to ascend a mountain for 
cooler weather as to journey northward. 
Now the first elevations beside a valley are 
usually low ones, foot-hills, outlying ridges or 
higher spurs. The plants that ascended these 
elevations, as the heat came on and proved too 
severe for their constitutions, were shriveled and 
burned then and there—the last battle ground and 
altar-places where were immolated the greater 
part of the vegetable creation of the period. 
the: tone survivors. 
Here and there straggling members of a family 
reaching a locality on the plain or part way up a 
mountain when the present equilibrium of seasons 
was established, found themselves suited to the 
environment—and it is the descendants of those 
plants that are the inhabitants of our plains and 
mountains to-day. 
These terminals of broken lines of development, 
