FOREWORD 



The books of reference for the botanical de- 

 scriptions are Gray's "Manual of Botany," 7th 

 edition, and Britton's "Manual of the Flora of 

 the Northern States and Canada.'- The pho- 

 tographs are the work of Mr. Carl Krebs of 

 Cleveland, Mr. Nathan R. Graves of Rochester, 

 and Mr. Wilson L. Conway of Milwaukee. 



