Josselyn Botanical Society 



17 



in a peculiarly plastic state, due perhaps to the sudden im- 

 petus to variation given by the great increase in their natural 

 habitat through the cutting of the forests. Besides the in- 

 tensifying of any tendency to vary, hybridization has been 

 frequent. Conversely, some of the asters and golden-rods 

 are among the few American species that have readily be- 

 come established in Europe, in competition with the plants 

 native there. 



In these various ways, then, a continual interchange is 

 in progress between the different floras of the world, the more 

 adaptable species spreading extensively, the specialized forms 

 being crowded out. It seems probable, therefore, that in the 

 course of a few centuries the basic elements of the flora of 

 the whole civilized world will be the same cosmopolitan 

 weeds, the native species forming only the local peculiarities 

 of any given region. 



