PREFACE ix 



Special acknowledgment is also made for the privilege of 

 using in this text various illustrations from Bergen's " Founda- 

 tions of Botany," Bergen and Caldwell's " Introduction to 

 Botany " and " Practical Botany," and Bergen and Davis's 

 " Principles of Botany." 



Acknowledgments are due to Dr. H. S. Conard of Grinnell 

 College for the critical reading of the preliminary manuscript 

 of Parts I and II and for criticisms and suggestions based 

 upon the use of the text, in typewritten form, with his own 

 classes. 



The author is also indebted to Dr. E. C. Jeffrey of Harvard 

 University for some of the microphotographs of woody and 

 herbaceous stems used in the text, and to Dr. W. J. V. Osterhout 

 of Harvard for valuable suggestions. 



