PREFACE. 



IF the present book is found to have any merit in its par- 

 ticular field, it will consist chiefly in its practicability. With 

 but few and clearly indicated exceptions, everything recom- 

 mended in it has been repeatedly tested and found effective 

 both by my students and myself. The book is the resultant 

 of six years of effort and experiment directed to this end with 

 classes of from eight to twelve students. 



The illustrations of the experiments are in every case from 

 photographs of experiments in successful operation. Such 

 pictures, while inferior in clearness of detail and perhaps in 

 artistic effect to good drawings, have at least this conspicuous 

 merit, that they may be accepted and followed with perfect 

 confidence. 



In developing the course and the experiments herein 

 recommended, I have tried to utilize, and, naturally, to 

 improve upon, the best work done by others in the same lines. 

 Little account is taken in these pages of the exact appliances 

 and methods with which the classical work of plant physiology 

 has been done, for the investigation phases of the subject lie 

 without the scope of this work, and they are, moreover, sum- 

 marized admirably in Pfeffer's great Handbook. But all 

 phases of plant physiology utilizable for purposes of general 

 education are meant to be included. The systematic attempt 

 to simplify physiological methods and appliances for student 

 use began, I believe, with Detmer's "Praktikum,' in iSS/> 

 was continued in Hansen's* "Physiologic'' and Schleichert's 



" Beobachtungen und Experimenten ' in 1890, in Oels's 



iii 



