ACKNOWLEDGMENTS.
The author desires to avail himself of this opportunity to tender his thanks to those under whose guidance he has worked while a student at the Johns Hopkins University, namely to Professors Remsen, Morse, Jones, and Andrews, and to Doctors Acree and Tingle for instruction in lecture room and laboratory.
He is especially indebted to Dr. S. F. Acree, at whose suggestion this research work was undertaken, for counsel and assistance in its prosecution.
He would also thank Messrs. Parke, Davis and Co., of Detroit, Mich., for the preparation of the crude material used in this investigation, and the U. S. Department of Agriculture, Washington, D. C., for electrotypes of figures 17, 18, and 19 in Bulletin No. 20, Division of Botany.