Human Factor in Plant Evolution 293 



streams raging torrents after heavy rainfalls and 

 when the snow melts, only to leave them shrunken 

 into insignificance in the heat of summer. This dis- 

 turbance of the water distribution necessarily affects 

 very strongly the vegetation of the region con- 

 cerned. Of perhaps as much interest scientifically 

 as practically, is the result of extensively reclaiming 

 swamp areas. The swamps and bogs are the haunts 

 of many of the rarest and most beautiful of our 

 native plants, which have taken refuge in these in- 

 accessible sanctuaries. The tamarack swamp, with 

 its beds of peat-mosses and dense undergrowth, was 

 the happy hunting ground of the botanist. Now 

 with the draining of the bogs, there are rapidly dis- 

 appearing many of our loveliest orchids, the car- 

 dinal flower, pitcher-plants, and hosts of other curi- 

 ous and beautiful botanical treasures. 



Introduction of Foreign Plants. The widespread 

 introduction of ornamental trees and garden flowers 

 into civilized countries has also much changed the 

 appearance of the vegetation in all of them. In any 

 long-settled community it is astonishing how little 

 of the vegetation which one encounters is really 

 native to it, or if so, has not been planted by man. 

 Indeed at present, if one wishes to see the unchanged 

 indigenous vegetation of any country, it is neces- 

 sary to seek the most remote and unsettled regions 

 of swamp, moor, or mountain. 



The origin of many cultivated plants, as we have 

 seen, is very obscure, and it is evident that most of 



