A SCHEMATIC REPRESENTATION OF THE WATER 

 RELATIONS OF PLANTS, A PEDAGOG- 

 ICAL SUGGESTION 



BURTON EDWARD LIVINGSTON 



The Johns Hopkins University, Baltimore, Md. 



The .extreme complexity of the relationships which determine 

 the moisture content of the growing regions and other active parts 

 of the ordinary plant renders it somewhat difficult to bring these 

 relationships clearly to the mental grasp of students of plant 

 physiology. The fundamental importance of these water rela- 

 tions is generally acknowledged, but current treatises as generally 

 fail to present anything like a logically balanced consideration of 

 the diverse conditions therein involved. The outline here pre- 

 sented was first prepared as an aid to research in this field and was 

 subsequently arranged in the form of a diagram, it is here given 

 the form of headings and sub-headings, a form of presentation 

 better adapted to the use of the printed page. Some of the evi- 

 dence upon which certain points are based has not yet been pub- 

 lished, but will shortly appear. The scheme makes no pre- 

 tense to completeness; it attempts to exhibit in barest outline 

 the main factors which appear to determine the moisture con- 

 ditions in the active parts of the ordinary rooted plant. 



An important pedagogical feature of this scheme is the clear- 

 ness with which it brings out the purely artificial character of 

 our conventional distinction between the organism on the one 

 hand and its environment on the other. The innumerable series 

 of chains of causes and effects, wherein the effect of one cause 

 is itself the cause of another effect, and so forth, reach into and 

 through the plant without reference to its spatial limitations. 

 Thus, the water in a "storage organ" is undoubtedly within the 

 plant and is nevertheless to be reckoned as an environmental con T 



214 



