x PREFACE TO THE FIRST EDITION 



side reading assignments and not as review questions. The 

 student should early get the idea that plant physiology is a subject 

 and not a book. 



The references at the ends of the chapters are intended to sup- 

 plement the text, and are not merely lists of articles cited in it. 

 Some students enjoy going a little deeper into a subject than 

 their fellows and for them these lists of references are appended. 

 The readings suggested are all in English as I have seldon found 

 that beginning students in America or England are able to handle 

 a foreign language profitably. References in a foreign tongue 

 seem to repel them rather than to attract. To gain the students' 

 interest, I have not hesitated to include in the list popular sum- 

 maries of a subject as well as the reviews found in the Botanical 

 Gazette and Science Progress. Completer bibliographies can always 

 be obtained from the articles cited. All that a real student needs 

 is to be placed at one end of the bibliographic trail. 



The use of the term " survival value" may need some explana- 

 tion. An effort has been made to get away from " adaptation" 

 which is anathema to most physiologists. We have all long recog- 

 nized it as a shorthand expression for which something better 

 was needed. I have hit upon the phrase " survival value" which 

 expresses the idea of the importance of a structure in evolution 

 without at the same time implying something further which we 

 do not intend. 



Agronomists may wish there was more mention of field crops, 

 horticulturists may lament the lack of horticultural illustrations, 

 and general physiologists may possibly decry the lack of references 

 to work done on the simpler plants and animals, but a book in 

 general plant physiology must be an introduction to all of its 

 branches; specialization can then follow later. 



No one writes a book without being indebted to all who have 

 gone before, and in writing a scientific textbook this is especially 

 true. To my colleagues who have helped with their photographs, 

 I am very grateful; and to Drs. Henry Hooker, 0. L. Inman, 

 Antoine Kozlowsky, C. J. Lyon, Wm. Seifriz, and R. H. True 

 who have read parts or all of the manuscript I owe my especial 

 thanks. This is scant gratitude for so valuable a service. 



Biological Abstracts, RAN RABER 



University of Pennsylvania, 

 May, 1928. 



