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. Newcombe 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. 
Cuas. H. Orts. 
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