106 THE AMERICAN BOTANIST 



Stances and occupies as nuich territory as it can conquer for 

 itself. But often line and, in many cases imperceptible dif- 

 ferences in soil or climate make an area unfitted for the sur- 

 vival of a given species though in no wise inhabitive to some 

 other. Thus have come ab(»ut the willow thickets, walnut 

 groves, oak forests, berry patches, alder swamps, sphagnum 

 bogs, wintergreen colonies and many more. Even one who 

 has liacl no botanical training recognizes the difiference be- 

 tween two such regions though often unable to state it in 

 wortls. He does not hunt for pitcher plants on hillsides nor 

 for sassafras in swamps. Among the upland forests ui pine, 

 oak, and hemlock we may find arbutus, sweet-fern, winter- 

 green, and huckleberries, while in the maple-covered low- 

 lands grow the bloodroot, hepatica, violet, and phlox. 



Although each species is at present spread as far as pos- 

 sible in every direction, various natural agencies may at any 

 time open new fields for further colonization. The great bar- 

 riers of the earth, however, such as mountain chains, deserts, 

 oceans and the like ultimately divide vegetation into fairly 

 distinct groups. Thus the flora of the Northeastern States 

 differs in its major aspects from that of the Gulf States, as 

 both differ from the flora of the Pacific Slope or of the 

 Great Plains. But while a given species rarely extends far 

 beyond the boundaries thus set. it is the usual thing to find 

 other species very much like it in adjoining regions. It is 

 likelv that all may have arisen from a common stock at some 

 time long in the past, but in adapting themselves to different 

 conditions have taken on different characteristics which for- 

 ever distinguish them. 



