SOME RECENTLY INTRODUCED WEEDS. 19 



tansy, tufted vetch, and many other European plants have in 

 America indigenous representatives ; but these American plants, 

 adapted through long centuries to their habitats along woodland 

 rivers, never show an inclination to take to the fields or the road- 

 sides, although plants imported from Europe and to all appear- 

 ances identical delight in the cultivated fields and the haimts of 

 man. In other words, as already stated, while the American 

 plant, unaccustomed to the ways of civilization until the recent 

 and still unfinished clearing of the forest, is unable readily to cope 

 with changed conditions, the European plant, through a long life 

 of competition with man, has developed a hard}^ stock which is 

 undaunted by the hardships of the roadside and the inhospitable 

 farm; 



This point is further emphasized by a comparison of our New 

 England flora with that of Great Britain. Of the species grow- 

 ing in the British Isles only above an altitude of 3,000 feet, i. e., 

 in the mountain country where the j^rimitive vegetation is but 

 little disturbed, 64 per cent are also native in the cold forests or 

 on the mountains of northern New England. But of the species 

 which occur everywhere at low altitudes and in the thickly-settled 

 and closely-farmed districts of England only 23 per cent are native 

 to New England as well, while more than 50 per cent have 

 become established in New England as weeds. Opposed to this 

 we have the striking fact that in temperate Europe barely 1 

 per cent of the wild plants have been introduced from the United 

 States. 



Besides the hardy character of the plants which come to us as 

 weeds from Europe there is another factor which must })e borne 

 in mind. Any organism transplanted from its original surround- 

 ings to a new but favorable region is inclined to increase in vigor 

 and powers of reproduction. The case of the rabbits in Australia 

 is now classic. Our own experiences with the English sparrow, 

 the brown-tail and the gypsy moth are examples nearer home. 

 The same principle holds with weeds. In Europe the marguerite 

 or daisy is rarely seen except in the gardens, but, once started in 

 America, it has overrun the Eastern States and is rapidly taking 

 as strong a hold in the West. A famous case — one of the few 

 in which we have squared accounts with our European cousins — 



