2 



unfortunately, was destroyed a few years ago, when he took up his res- 

 idence in Roekford, Illinois. Since the year 1374, when he described 

 his first Willow in The American Naturalist, all the collections of 

 Willows made in North America have been studied by him; he has de- 

 scribed the California species in Brewer & Watson's Botany of Cali- 

 fornia, the southwestern species collected by Rothrock in the sixth 

 volume of Wheeler's Reports, the Coloraao species in Coulter's Manual 

 of the Botany of the Rocky Mountain Region, ana the species of the 

 eastern states in the last edition of Grays Manual, and has contri- 

 buted to botanical journals many papers upon the American species of 

 the genus. 



The specimens which are figurea in this work have ail been se- 

 lectee by Mr. Bebo, and I take this opportunity to acknowledge my 

 great indebtedness for the advice anu assistance which he hds freely 

 given me during the last fifteen years. 



