PREFACE. xiii 



to him we are al^o indebted for many plants from the mountains 

 of Virginia, and from Alabama. 



From Indiana, Dr. Clapp of New Albany has supplied us with 

 many interesting plants. 



From Ohio, Mr. T. G. Lea, Mr. Wm. S. Sullivant, Mr. 

 John Samples, and Dr. Paddock, are the chief contributors. 



From Michigan, Dr. Houghton and Dr. Wright have fur- 

 nished us with numerous plants : to the former we are under ad- 

 ditional obligations for a parcel of plants collected towards the 

 sources of the Mississippi. From the same region we have an 

 interesting collection made by Major D. B. Dou<3lass during the 

 Expedition of Gov. Cass. 



To Dr. Pitcher we are also indebted for many plants collected 

 in the northern part of Michigan, the shores of Lake Superior, &c. 

 From Milwaukie, Wisconsin Territory, we have received a col- 

 lection of plants from Dr. Lapham. To Dr. Holmes of Mon- 

 treal, Mrs. Percival, Mr. and Mrs. Sheppard, and Mr. McCrae, 

 we are indebted for numerous plants from Canada. 



The collection made by Dr. Edwin James in Major Long's 

 Expedition to the Rocky Mountains, of which an account has 

 been given in the Annals of the Lyceum of Natural History, 

 has been very useful to us. 



The authors venture to hope that their obliging correspondents 

 will still continue to render their assistance in the farther prose- 

 cution of this work, by sending the rarer plants of their res- 

 pective districts, with such notes and observations as they may 

 deem important. 



Since the publication of the earlier portions of this volume, our 

 opportunities for examining the herbaria of original authors have 

 been very much extended ; and the necessary corrections and 

 changes we have been obliged to make on this account, together 

 with some additions from works recently published and from 

 materials since received, are given in the appended Supplement. 

 We trust these investigations will give this work an important 

 value in respect to the authenticity of the specific names, and that 

 future changes of the kind will not be to any considerable extent 

 necessary. 



