222 NUTRITIVE METABOLISM 



chloroplasts, and a careful examination would doubtless bring 

 many other instances of the same kind to light. 



Furthermore it is not to be taken' for granted that any function 

 of the cell is the specific action of the organ in which the results 

 of the process become manifest. Thus the wall apparently 

 secreted by the cytoplasm, is not formed in the absence of the 

 nucleus, which may not lay down this membrane by its own 

 separate action. Again the assumption that the nucleus is the 

 seat or especial organ of the synthetic processes, and the cyto- 

 plasm the arena for the liberation of energy may not be maintained 

 in view of the facts just related. Nor can the function of nutri- 

 tion, or even absorption be ascribed to any region of the cell. 

 While the absorption of material must take place through the 

 outer plasmatic membrane yet the energy for the attractive process 

 is furnished at some distance from it, and in fact the whole cyto- 

 plasmic mass may be regarded as an osmotic membrane. 1 



The components of the cell are therefore to be regarded as 

 mutually interdependent physiologically, although it is to be con- 

 ceded that the nucleus occupies a directive position in all mor- 

 phological constructive operations of the protoplast, a familiar 

 instance of which is to be seen in the unequal thickening of cell 

 walls according the proximity of the nucleus. Furthermore it is 

 supposed that the nucleus is a primary factor in transmitting the 

 qualities of the species from one individual to another in lineal 

 succession, yet the action of the cytoplasm has not been wholly 

 excluded in any experimental evidence hitherto offered. 



291. Nutritive Elements Obtained from the Soil by Green Plants. 

 A determination of the elements taken from the soil by green 

 plants may be made by cultures in which plants are grown in 

 some neutral substratum like quartz sand, or distilled water, to 

 which is added solutions of the various substances to be tested. 

 The results of such investigations are often obscure, owing to 



1 See conflicting views, Wilson, E. B. The cell in development and inheritance, 

 p. 341. 1900. 



Pfeffer, W. Physiology of Plants. I : 50. 1900. 



