DEPARTMENT OF BOTANICAL RESEARCH. 



59 



Cfay or ^ 



wooden wall 



following paragraph, much important information may be gained as 

 to the time relation in osmosis. Osmosis has been chiefly studied 

 from a thermodynamic viewpoint, consideration being given to equi- 

 libria rather than to rate of action, although the speed of penetration 



of membranes and the duration of 



the processes have always been up- 

 permost in the mind of the physiol- 

 ogist. Some of the possibilities in 

 this field are suggested by the ac- 

 tion of a colloidal cell filled with 

 water and immersed in water. 



In the beginning the action must 

 consist partly of hydration or swell- 

 ing of the plasmatic layer by water 

 taken up from the cell-contents 

 and drawn in through the clay 

 wall. At the same time some of 

 the colloidal electrolytes of the 

 plasma are passing into solution in 

 the cell-sap, with a resultant os- 

 motic action of the dissociated 

 material. The endosmosis taking 

 place increases the contents, the 

 surplus passing out through the de- 

 livery tube at a rate which increases 

 for 4 to 7 days, after which a grad- 

 ual lessening of the rate takes place 

 which, however, may allow as much 

 action on the fortieth day as on the 

 first, which would be about one- 

 third of the maximum shown on 

 the fifth or sixth dsij. The plot- 

 ting of the varying rates results in 

 a graph of the type of the "bio- 

 logical curve," by which the activ- 

 ities of a cell or organism may be 

 expressed during its lifetime. The 

 action of the cell depends chiefly 

 on the fact that the material of 

 the gel or "plasma" of the cell, 

 which has an approximate dry 

 weight of 1 gram, passes slowly into solution, and, being composed of 

 colloidal electrolytes, osmotic activity ensues, which causes water to 

 enter the cell, with the expulsion of an equivalent amount. The loss 

 of water in this manner implies a loss of dissolved material and is 

 ghly suggestive of certain forms of secretion in plant organs. 



-^4 



Section of an artificial cell arranged to 

 show contlniiing osmotic action of col- 

 loidal layers as in a living cell. Such 

 cells filled with water showed positive 

 osmose for periods of two or three 

 months at a rate varying in a "biolog- 

 ical curve." 



