PREFACE. V 



the species has taken place. It would require a 

 new edition rather than a supplement, to indi- 

 cate all of these changes, and any one who is 

 conversant with the Genera as determined 

 by Schreber and Willdenow, will readily com- 

 prehend the principles on which these chan- 

 ges have been made, and the characters of the 

 new genera which have been adopted or pro- 

 posed. Mo^t of the alterations which have been 

 made in American plants will be found in Nut- 

 tali^s "Genera of North American Plants," or 

 in the valuable Flora of the Northern States 

 now publishing by Dr. Torrey of New-York. 



If however the friends who have hitherto by 

 their contributions added so much to the value 



of this work shall not find their patience ex- 

 hausted; if they and if others who may be at- 

 tracted to the study of this interesting science 

 will continue to communicate to the author such 

 plants as he may appear to have omitted, such 

 as he may have inaccurately or imperfectly de- 

 scribed, and will point out errors of any kind 

 which he may have committed, he may hope at 

 a future day to present this work in a form more 

 worthy of their approbation. 



To those friends he feels gratified to make 

 public his acknowledgements. With the late 

 Dr. Muhlenberg of Lancaster, Penn. he was 

 accustomed for many years to compare and 

 collate the plants of Carolina and Pennsylva- 

 nia, and derived from this correspondence 



