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Bulletin 3 



which never become weeds. Thus Plantago major L,., was 

 introduced with the earliest settlers and is one of the com- 

 monest of weeds. Tfie native plant, P. major, var. asiatica 

 (L.) Dene., is found upon the gravelly beaches and river 

 banks from Labrador and Quebec westward across the conti- 

 nent in the coniferous belt, but neither becoming a dooryard 

 weed, nor showing any tendency to spread to the fields and 

 pastures. Achillea Millefolium L., and A. borealis Bong., 

 illustrate the same rule. A. borealis is an indigenous plant, 

 growing on the gravelly beaches along the lakes and rivers 

 across the northern part of North America, but never occur- 

 ring in the fields and pastures where the European A. Mille- 

 folium is found, although, the latter species does spread to 

 the river banks. Other instances of such distribution are : 

 Taraxacum officinale Weber and T. ceratophorum (Ledeb.) 

 DC; Cynoglossum officinale L., and C. boreale Fernald ; 

 Tanacetum vulgare L,., and T. huronense Nutt. In study- 

 ing the introduced flora the question naturally arises, then, 

 how does it happen that these Old-World plants can compete 

 so successfully with our own species ? The explanation 

 seems to lie in the different habitats of the related species. 

 The indigenous plants usually grow in gravelly beaches or 

 natural meadows, where in the course of many years they 

 have become specialized products of a certain set of condi- 

 tions and unable to adapt themselves readily to changes in 

 their environment. The introduced plants, on the other 

 hand, come from an old and closely farmed country where 

 wild plants find scant room in which to grow. Hence, from 

 centuries of fighting against civilization, these weeds have 

 become extremely adaptable and able to flourish in the most 

 unfavorable surroundings. Such plants, when introduced 

 into the comparatively luxurious conditions of a new country, 

 run riot and crowd out the native species, which, if left to 

 themselves, might have developed weedy tendencies. In- 

 deed the native golden-rods, asters, blackberries and violets 

 already show signs of this stage of development. These 

 genera are represented by a few stable species in the undis- 

 turbed regions such as Gaspe and northern Maine, but in the 

 longer settled regions to the south and west, they seem to be 



