PREFACE Xin 



248) originated with Dr. Gundersen, but has been modi- 

 fied, as here printed, in certain details for which the 

 author alone is responsible. Grateful acknowledgment is 

 made to Dr. Ralph E. Cleland for photo prints of Figs. 

 74 and 75 from negatives made by him on the summit 

 of Mt. Madison (Adirondacks) ; and to Prof. Harvey 

 W. Shimer, author, and The Macmillan Co., publisher, 

 for permission to reproduce Fig. 66. 



If the following pages shall prove to be a source of re- 

 liable and readable elementary information to those in- 

 terested in the subjects treated, the object of the book 

 will be accomplished. 



Brooklyn Botanic Garden, 

 March 25, 1920. 



C. Stuart Gager. 



