PREFACE. 



This work is designed as a compendious Flora of the Northern 

 portion of the United States, for the use of students and of practical 

 botanists. 



The first edition (published in 1848) was hastily prepared to sup- 

 ply a pressing want. Its plan, having been generally approved, has 

 not been altered, although the work has been to a great extent twice 

 rewritten, and the geographical range extended. The second edition, 

 much altered, appeared in 1856. The third and fourth were merely 

 revised upon the stereotype plates, and some pages added, especially 

 to the latter. 



The Garden Botany, an Introduction to a Knowledge of the 

 Common Cultivated Plants, which was prefixed to this fourth edition 

 in 1863, is excluded from the present edition, and is to be incor- 

 porated into a simpler and more elementary work, but of wider 

 scope, designed especially for school instruction, and for those inter- 

 ested in cultivation, — entitled Field, Forest, and Garden Botany. 



In the present edition it has been found also expedient to remand 

 to a supplementary volume the Mosses and Liverworts, so carefully 

 and generously elaborated for the previous editions of this work by 

 my friend, "Wm. S. Sullivant, Esq. It is hoped that the Lichenes, 

 if not all the other orders of the Lower Cryptogamia, may be added 

 to this supplementary volume, so that our students may extend 

 their studies into these more recondite and difficult departments of 

 Botany.* 



* The following important aids, moreover, are already provided, viz. The 

 Icones Muscot-um, or Figures and Descriptions of most of t/iose Mosses peculiar to 



