PREFACE. tt 



reference to the special needs of those students to whom 

 the larger works and the current journals are not easily 

 accessible. The same rule has been largely followed in 

 the treatment of citations from authorities. Where it has 

 been possible to do so without too great sacrifice of 

 space, the phraseology of the original reference has been 

 given. 



In the preparation of this volume the author has had at 

 many steps the wise counsel of his teacher and associate, 

 Professor ASA GRAY, to whom he wishes to make his 

 grateful acknowledgments. 



In the proof-reading, verification of references, and In- 

 dex, Mr. W. W. NOLEN, Assistant in Biology, has rendered 

 aid of great value. His painstaking and good judgment 

 have lightened in every way a formidable and burdensome 

 task. 



GEORGE LINCOLN GOODALE. 



BOTANIC GARDEN OF HARVARD UNIVERSITY, 

 CAMBRIDGE, MASS., August, 1&86. 



