ACKNOWLEDGMENTS 



Grateful acknowledgment is hereby made to Miss Sarah 

 Phelps, who has done most of the inking in and given life to 

 the author's pencil-drawings ; to Mr. J. H. Ehlers for his valuable 

 assistance in the preparation of many of the drawings and in the 

 collection of working material; to Prof. Henri Hus, who has 

 read all of the proof and who has at various times rendered 

 valuable assistance; to Prof. F. C. Newcom'be and to Prof. 

 Ernst Bessey for the loan of sheets from the herbariums of the 

 University of Michigan and Michigan Agricultural College; and 

 especially to Prof. Geo. P. Burns in whose inspiration this 

 bulletin had its inception and under whose direction the work has 

 progressed to completion. 



CHAS. H. OTIS. 



