A CHART OF PHYSIOLOGICAL PROCESSES: AN AID TO 

 THE TEACHING OF PLANT PHYSIOLOGY^ 



WILLIAM E. LAWRENCE 

 Oregon Agricultural College, Corvallis, Oregon 



It is often difficult for the student of plant physiology to under- 

 stand the extreme complexity and the delicate conditions of 

 equilibrium in the protoplasmic mechanism. This is perhaps due 

 to the many close relationships and the intricate interdependence 

 of the processes, which constitute a chemical equilibrium not suffi- 

 ciently emphasized by most texts. In the teaching of plant physi- 

 ology, as of many other subjects, some graphic representation of 

 the ideas involved frequently gives a much firmer and clearer 

 mental grasp than that attained by any other method, and the 

 writer has found that a diagram of the physiological life-cycle is 

 of great benefit, not only for the beginner but for the more ad- 

 vanced student as well. It is often necessary to place so much 

 emphasis on the chemical and physical individuaUty of each physi- 

 ological process, that it is difficult to impress the student with 

 the idea that these processes are also very intimately associated 

 and that their sequence is a chemical and physical one, so that 

 plant physiology is in danger of being interpreted as a collection of 

 so many independent processes. If, however, the student can 

 secure a mental perspective of all these physiological processes 

 in relation to each other and in relation to the life-cycle of the 

 whole plant, he will have one of the best foundations for a thor- 

 ough understanding of plant activities. 



The chart herewith presented attempts to meet this need. Of 

 course it should not be given to the student in its complete form 

 at the beginning of his study. Neither should the reader feel 

 discouraged if his first glance gives him the impression that it is 



' Contribution from the Department of Botany and Plant Pathology, Oregon 

 Agricultural College, No. 2. 



256 



