14 PREFACE. 



For its purpose, the present geographical limitation is, on the 

 whole, the best, — especially since the botany of the States south of 

 our district has been so well provided for by my friend Dr. Chap- 

 man's Flora of the Southern States, issued by the same publishers. 

 The southern boundary here adopted coincides better than any other 

 geographical line with the natural division between the cooler-tem- 

 perate and the warm-temperate vegetation of the United States ; 

 very few characteristically Southern plants occurring north of it, 

 and those only on the low coast of Virginia, in the Dismal Swamp, 

 &c. Our western limit, also, while it includes a considerable prairie 

 vegetation, excludes nearly all the plants peculiar to the great West- 

 ern woodless plains, which approach our borders in Iowa and Mis- 

 souri. Our northern boundary, being that of the United States, 

 varies through about five degrees of latitude, and nearly embraces 

 Canada proper on the east and on the west, so that nearly all the 

 plants of Canada East on this side of the St. Lawrence, as well 

 as those of the deep peninsula of Canada West, will be found in 

 this volume.* 



I have here endeavored to indicate, briefly and generally, the dis- 

 trict in which each species occurs, or in which it most abounds, in 

 the following manner : 1. When the principal area of a species is 

 southward rather than northward, I generally give first its northern 

 limit, so far as known to me, if within the United States, and then 

 its southern limit if within our boundaries, or add that it extends 

 southward, meaning thereby that the species in question occurs in 

 the States south of Virginia or Kentucky. Thus Magnolia glauca, 

 p. 49, a prevailingly Southern species, but which is sparingly found as 

 far north as Massachusetts, is recorded as growing " near Cape Ann 

 and New York southward, near the coa-t " ; M. acuminata, " W. 

 New York to Ohio and southward," &c. While in species of northern 



* For the geographical statistics of our botany, see three articles in The 

 American Journal of Science and Arts, Second Series, Vol. XXII. and Vol. XXIII. 

 1856-57. 



