TO 
JOHN TORREY, M. D. 
CORRESP. MEMBER OF THE LINN.KAN SOCIETY, ETC., 
THIS VOLUME IS DEDICATED 
BY 
THE AUTHOR, 
IN GRATEFUL ACKNOWLEDGMENT 
OF THE FRIENDSHIP WHICH HAS HONORED AND THE COUNSEL 
WHICH HAS AIDED HIM FROM THE COMMENCEMENT OF 
HIS BOTANICAL PURSUITS. 
Cambridge, January 1, 1848. 
