156 



ClIAPTEl; X. 



CHEMICAL AND PHYSIOLOGICAL STUDIES IN 

 CONNECTION WITH THE CELL. 



It is now necessary to direct attention to some of the more 

 important chemical and physiological processes to he observed in 

 the living plant, processes which are, moreover, to be looked 

 upon as the reflection on a large scale of what is going on in 

 each living cell. 



Some of these processes may be demonstrated in the cell itself 

 by the use of suitable reagents, and yet others are only to be 

 detected by the employment of experimental methods involving 

 the use of the whole, or, at any rate, a large part of a plant. 

 It was, moreover, seen in Chapter i. that the \'itality of the 

 protoplasm depends upon the maintenance of certain conditions, 

 such as an adequate supply of water and oxygen and the co- 

 existence of a suitaljle temperature, and also that protoplasmic 

 continuity between the living cells in a cell-communit}- was 

 a necessary factor. Therefore, in the performance of laboratory 

 experiments upon plants, or parts of plants, it is often essential to 

 ensure the presence of those conditions under which the plant 

 investigated exists in nature ; otherwise the results of experiment 

 will be inaccurate and hardly expressions of natural processes. 



A. The General Chemistry and Physiology of the Cell. 



Before proceeding to the detailed study of some of the more 

 readily demonstrable chemical processes taking place in the cell, 

 it is advisable to have an outline of the chemistry and physiology 

 of that structure, looked at from a general point of view. The 

 protoplasmic contents of a typical assimilating cell maj' be looked 

 upon as a very efficient energy-transformer and utiliser, in which 

 the principle of the conservation of energy holds good, just as it 

 does whatever the working substance may be. 



