PREFACE vil 



electricity to plants, and revised the entire chapter dealing with 

 that subject ; Dr. R. H. True, of Harvard University, has aided 

 materially with suggestions in regard to the chapter dealing with 

 the relations of plants to chemicals ; Mr. A. F. Woods, of the 

 Division of Vegetable Pathology and Physiology, U. S. Depart- 

 ment of Agriculture, kindly furnished me with results of investi- 

 gations of his own, and other members of the staff, in advance 

 of their publication ; Dr. H. M. Richards, of Barnard College, 

 Columbia University, compiled and corrected the greater part of 

 the appendix ; I am also indebted to Dr. G. T. Moore, of Dart- 

 mouth College, Professor Francis E. Lloyd, of Teachers College, 

 Columbia University, and to my colleagues in the New York 

 Botanical Garden for valued assistance. In justice to these con- 

 tributors, it is to be said that revision of the final proofs has rested 

 with the author, who holds himself responsible for the contents 

 of the entire volume. 



The Author. 

 New York Botanical Garden, April 27, 1901. 



