92 Proceedings of Indiana Academy of Science. 
the student the impression that osmosis takes place only in root hairs | 
and is concerned only with supplying the plant with water and mineral 
food. The student should be led to connect osmosis with his knowledge 
of cell structure and to see the general nature and importance of the 
process. All the living matter (protoplasm) in the plant or animal body 
is disposed in definite units (cells), whose unity is determined by the 
plasma membrane. The whole normal contact of the cell with its physio- 
logical environment—food, water, soil, air, digestive fluids, other cells, 
etc.—is defined and regulated, in so far as it is regulated at all, by 
this membrane. Thus, it is seen that all the life processes—respiration, 
photosynthesis, imbibition by living tissues, transpiration, secretion, ex- 
cretion, ete.—which involve the exchange of fluids between the cell and 
its environment, depend upon the selective influence of semipermeable 
membranes. 
I take this opportunity to acknowledge valuable assistance given me 
in the study of this problem by Professor O. W. Brown of the Depart- 
ment of Chemistry, Indiana University. 
REFERENCES. 
It is not deemed necessary to give here a detailed biblicgraphy 
Standard texts will illustrate the defects pointed out; the historical side 
of the question is given in most good texts on physical chemistry. Kah- 
lenberg’s work is described in the Journal of Physical Chemistry, Vol- 
ume 10. 
