vi Preface 



from plants which are familiar and directly useful. By 

 maintaining some direct contact with practical problems, 

 interest is aroused for further desirable fundamental prepa- 

 ration. " The idea that useful knowledge cannot be cultural 

 must be dismissed. . . . Every possible application must 

 be made of each abstract principle." (Eliot, " The Conflict 

 between Individualism and Collectivism in a Democracy," 

 page 66.) - % 



In the field of pure physiology, there are recent texts 

 and guides embodying much of what is considered best 

 in the modern content and attitude of the science. An 

 elaboration of the methods of quantitative study is there 

 indicated, and stress is laid on the materials and energy 

 involved in plant activity. Such books will be consulted 

 with much profit. 



In selecting from the great amount of available material 

 that which has seemed to be most suitable for the present 

 purpose, consideration has been given the fact that in many 

 colleges general courses are offered, not only in such dis- 

 tinctively plant lines as agronomy, horticulture, and breed- 

 ing, but likewise in fields overlapping physiology, or partially 

 included in this subject, such as soils, bacteriology, pathol- 

 ogy, and genetics. The subject-matter included is intended 

 to be sufficient for a course of one-half year involving two 

 recitations and two laboratory periods ; but it may be 

 made the basis of a shorter course by suitable selection of 

 material, or of a longer course by an extension of the col- 

 lateral work. 



In the preparation of this text I have used freely any 

 available source of information. The subject-matter has 

 been presented at one time or another in class work. I am 

 indebted to Mr. Lewis Knudson, Instructor in Plant Physi- 



