BOTANICAL GEOGRAPHY. 31 



Why have we so few Crucifera, UmbelUfera 

 and Narcissides, compared to Europe and Af- 

 rica ? 



Why are the two shores of North America, 

 east and west, so unHke to each other in vege- 

 tation ? 



These queries and others of a similar nature 

 may exercise the ingenuity of speculative Bo- 

 tanists, or amuse their idle hours; but they are 

 facts and as such deserve our notice. 



Another interesting study is that of our na- 

 turahzed plants. We have so many that they 

 appear to invade the fields and drive out the na- 

 tive plants in some instances ; but it is by no 

 means certain but that some deemed natura- 

 lized, were not really native. Such at least 

 must have been the case with Verbascum thap- 

 siis^ Hypericum perforatum, Dauciis carota, 

 Anthemis cotula, Origarm'm vulgare, &c. 1 

 gave a long list of the naturalized plants in my 

 dissertation of 1808, some have since disappear- 

 ed, while others have appeared instead out of 

 gardens. But few American plants have be- 

 come spontaneous in Europe, Phytolaca decan- 

 dra and Cenotis canadensis are mentioned as 

 such ; but we have received several hundreds, 

 besides some few from the Antilles and inland 

 Decandole has properly stated that naturalized 

 plants even when not spontaneous, but exten- 

 sively cultivated in the open air ought to be ad- 

 ded to every general flora, and Eaton has fol- 

 lowed that advice with us. 



It appears that even previous to the discovery 

 of America by Columbus, our Indian tribes had 

 received or imported from abroad or the South, 

 several trees and plants. I have at least evi- 

 dently ascertained historically that this was 



