Chap, vi The Metabolic Processes 



379 



air, we need say here only that the authors show that with 

 liquids ' the flow of the diffusing substance . . . may go 

 on almost as rapidly through the multi-perforate septum, 

 as if no closing membrane were present ' (Phil. Trans., 

 B. 193, p. 281). 



It is probable that the protoplasm is more intimately 

 concerned in the matter than these purely physical ex- 

 planations allow, that, in fact, by a process something like 

 a modified secretion the protoplasm takes up the sugar from 

 the cell sap and passes it on into the contiguous cells, 

 the action starting in the cells abutting on that in which the 

 transformation into starch first occurs. The protoplasmic 

 threads on this hypothesis not only constitute the paths 

 for the translocation, but serve also to transmit a stimulus 

 from the cell in which a weakening of the sugar content 

 is set up to the contiguous ones which contain a greater 

 quantity. The protoplasmic secretory activity is thus a 

 response to the stimulation. 



At the end of the century these views remained still in 

 the region of speculation, and but little that was satis- 

 factory was definitely ascertained as to the forces causing 

 the translocation. Very little experimental work bore 

 upon the point, but it was ascertained that translocation 

 from the endosperm of a germinating seed goes on to 

 completeness in the absence of the embryo if the latter 

 is replaced by some absorbing substance such as a plug 

 of gypsum, though it does not progress so rapidly. 

 Hansteen in 1894 and Puriewitsch in 1897 were both able 

 to prove this. Their experiments proved further that this 

 depletion of the endosperm is not due to diffusion only, 

 for it was stopped when the germinating seed was moistened 

 with glycerine or a solution of nitre instead of with water. 



Deposition of Reserve Materials. The translocation 

 of the newly-constructed organic substance leads necessarily 

 to two different series of events. The first of these, the 



