PRKFACE. 15 



range, the southern limits are mentioned ; as Anemone Pennsylvan- 

 ica, ♦' W. New EngUmd to Illinois and northwestward." And so 

 of Western plants ; e. g. Isopyruin bilernutinn, p. 44, " Ohio to 

 Illinois, Kentucky, and westward"; Amorpha canescens, p. 130, 

 "Michigan to Wisconsin and southwestward." But this rule has not 

 always heen closely adhered to. 2. AVhcre no habitat or range is 

 mentioned, the species is supposed to be diffused over our whole 

 area, or nearly so, and usually beyond it. 3. AVhen the species is 

 quite local or rare, the special habitat is given ; e. g. Veslcaria 

 Shortii, p. 73, and Alyssum Lescurii, p. 72 ; Sidlivantia Ohionis, 

 p. 1G9, &,c. Except in such cases, or when the known geographical 

 range of a species has been recently extended, the want of space has 

 generally demanded the omission of particular stations, which are so 

 appropriately given in local Floras and in more detailed works, but 

 for which there is no room in a manual like this. 



For the same reason, I could not here undertake to specify the 

 range of those species which extend beyond the geographical limits 

 of this work, or beyond the United States. Nevertheless, to facili- 

 tate the comparison of our American flora with that of Europe, I 

 have appended the mark (Eu.) to those species which are indi- 

 genous to both. 



Distinction betaveen Introduced and Indigenous Spe- 

 cies. Foreign plants which have become denizens of the soil have 

 to be described along with the genuine indigenous members of our 

 flora ; but the introduced species are distinguished by the specific 

 name being printed in a different type, namely, in small capitals,* 

 while the names of the indigenous species are in iieavier, antique 

 letter-t Moreover, the country from which they came is specified 

 (mostly Europe), as well as the nature of the denizenship. That is, 

 following the suggestions of M. Alphonse De Candolle, I have clas- 

 sified our introduced plants as well as I could into two sorts, the 



* For example, uiukr Kanuuculus, R. ulmiosls, ackis, &c., p. 43. 

 t For exaaijile, R. repens, on the baine page. 



