INTRODUCTION. 



3 



sents the extent, position, and minute branching of the root system 

 more accurately than a photograph. This is especially true of the more 

 extensive root systems, for here, even under the most favorable con- 

 ditions, the photograph is always made at the expense of detail, many 

 of the finer branches and root-endings being obscured. 



During the course of these investigations the writer has become 

 greatly indebted to the following persons for faithful assistance in the 

 pursuance of this work. It is a pleasure to acknowledge here the 

 indebtedness to my students, Messrs. F. C. Jean and Alvin Goke, for 

 much help in the excavation of the plants, and to Miss Annie Mogen- 

 sen and Mrs. F. C. Jean for their assistance in drawing many of the 

 root systems. I wish also to acknowledge the helpful suggestions and 

 encouragement given by Dr. F. E. Clements and Dr. R. J. Pool 

 throughout the period of the work. To Professor T. J. Fitzpatrick 

 I am also indebted for careful reading of the manuscript and proof. 



