378 THE CANADIAN NATURALIST. [DeC. 



that were tlie country to resume its preadamite condition they 

 would probably soon disappear. Adventive plants form a nume- 

 rous class, embracing most of those weeds which confine themselves 

 to the vicinity of dwellings and barns, and to cultivated grounds. 

 The niust;irds and the corncockle, familiar pests on many eastern 

 farms, and the flax, carrot, parsnip, and artichoke, illustrate the 

 group. 



Those introduced species, which have freely spread themselves 

 throughout the settled parts of the country, and which, though 

 domesticated through the agency of man, are probably quite 

 independent of him for existence, come under the category of 

 naturalized plants. The buttercup, clover, Canada thistle and 

 sheep sorrel, strikingly exemplify this extensive group. 



The remaining groups require a more attentive consideration. 

 All of the species referred to them are indigenous to this country ; 

 some to the settled, others to the remote districts. With many 

 individual plants of some of the species it forms a question 

 whether their introduced habit indicates a foreign origin or results 

 from a tendency of the indigenous plant to abnormally spread. 

 In certain instances the known limitecl distribution of the species, 

 in its indigenous form, dispels any doubt. For example, around 

 Lake Superior. Agassiz chronicles as native, or probably so, 

 species whose habits, in the settled parts of the country, evince a 

 decidedly exotic origin. Where, however, the range of both forms 

 is extensive, indicating the limits of each is impx-acticable. It is 

 indeed possible that not only have the rambles of the native species 

 frequently placed them side by side with the domesticated plants, 

 and probably quite undistinguishable from them, but that in some 

 instances the species, though common to Europe and America, 

 have no introduced representatives here ; and that individuals of 

 these species, which have the habits of exotics, are in reality 

 indigenes which have wandered beyond their natural homes. 



A que'^tion, replete with interest, arises in connection with 

 these naturalized plants. Have changes of climate and of other 

 conditions in the long lapse of years impressed new specific char- 

 acters on the individuals of any species, or, if not, have they pro- 

 duced any permanent varieties ? If even the latter were the case, 

 it seems probable that not only might varieties be different on 

 difi'erent continents, but the migration of these varieties might also 

 lead to specific changes. Let the imagination trace the wander- 

 ings of one of these little plants under such circumstances. 



