18n9.] DRUMMOND — ON SPREADING PLANTS. 379 



Probably of a spreading habit in its native country, it emigrates, 

 through one of the innumerable channels constantly open, to a 

 foreign chine, where it becomes established, and where, in conse- 

 quence of a change of conditions, some slight but permanent 

 alteration is effected in its characters. The plant thrives, and in 

 the lapse of years becomes a widely distributed weed. Another 

 emigration takes place thence to a country where climatal and 

 other conditions are different from those of either its native country 

 or last adopted home. A more marked variety results. In the 

 course of long time this variety appears on another continent, to 

 be subjected to farther changes, which so destroy the identity of 

 the plant that a botanist only acquainted with the species in its 

 native clime, on seeing its wandering individuals here, hails the 

 discovery of an allied plant requiring a place in specific nomen- 

 clature. It is, however, a suggestive enquiry whether if this new 

 species or the variety were to find a footing in the country whence 

 its progenitors came, it would retain its identity as a species or 

 variety. The whole subject merits some investigation as to how 

 far, in any respect, climatic or other differences produce permanent 

 change. I cannot, however, help here recalling some analogous 

 cases. The inland maritime plants, growing on the 

 shores of the Great Lakes and elsewhere, have been subjected to 

 a great change in their conditions of growth without any corres- 

 ponding alteration in the distinctive characters of the species. 

 Similar instances are recorded in the insect fauna of Lake 

 Superior, and our attention has lately been drawn to Pieris rapm, 

 an intruding butterfly from Europe, extensively naturalized in 

 the Province of Quebec, which here even feeds on a plant differ- 

 ent from th.'it which constitutes its food on the other side of the 

 Atlantic, and yet retains its specific features unchanged. 



In enumerating, in the catalogue below, species which have both 

 indigenous and introduced representatives in the country, I briefly 

 indicate the provincial range and habits of each plant as far as 

 known. Our knowledge of the habits and distribution of the grasses 

 in Ontario and Quebec is, however, so limited that I enumerate, 

 without any accompanying notes, such species as are probably 

 referable to this catalogue. Indeed, with respect to both this 

 and the other catalogues, I shall be glad to have the aid of 

 botanical friends in rendering our knowledge of the habits and 

 range of all of the spreading and naturalized plants more com- 

 plete. 



