xii Preface by the Editor 



discussions and demonstrations to a form suitable for 

 permanent record, together with certain other alterations 

 which have been duly submitted to the author. The 

 original phraseology has been preserved as far as pos- 

 sible. The editor wishes to acknowledge material as- 

 sistance in this work from Miss A. M. Vail, Librarian of 

 the New York Botanical Garden. 



D. T. MacDougal. 



New Yorh Botanical Garden, October, 190^. 



