IV PREFACE, 
in Kuropean herbaria is earnestly commended to those botanists 
who are not familiar with the method of types or who are opposed 
to its application. 
Opportunity was given by various curators for the examination of 
specimens in their charge. Acknowledgment is made, however, to 
B. Daydon Jackson, Carl A. M. Lindman, P. IH. Lecomte, and A. B. 
Rendle for special courtesies and assistance rendered by them in 
facilitating the examination of collections in their charge. 
FREDERICK V. COvILLE, 
Curator of the United States National Herbariwn. 
