TO 



JOHN TORKEY, M.D. F.L.S., ETC. 



PROFESSOR OF CHEMISTRY AND BOTANY, 

 IN THE UNIVERSITY OF THE STATE OF NEW YORK, 



AND 



ASA GRAY, M.D. ETC., 



PROFESSOR OF NATURAL HISTORY, 



IN HARVARD UNIVERSITY, 



WHOSE NAMES AR.E IDENTIFIED WITH 



NORTH AMERICAN BOTANY, 



THIS WORK 



IS RESPECTFULLY DEDICATED 



BY THEIR FRIEND 



THE AUTHOR. 





