3 88 



BOTANICAL GAZETTE 



[may 





not the case with onion and cycad membranes. The differences in 

 rate in opposite directions through a membrane have long been 

 known to workers with animal membranes. Matteucci and 

 Cima (21) in 1845 observed it with the skin of the frog and eel. 

 Cohnheim (9), according to Hamburger, ascribed the same 

 phenomenon to the living action of the intestinal membrane. 

 Hamburger (14) showed that this behavior was not restricted to 

 living membranes, but that non-living animal membranes gave 

 similar results; in fact, he prepared artificial membranes from 

 parchment with layers of collodion, chromgelatin, and chromal- 

 bumen that were more permeable in one direction than in the 

 other. He ascribes this to the "double" nature of the membrane, 

 and the writer's results offer evidence in favor of Hamburger's 

 interpretation. If this difference in rate is due to the presence of 

 double membranes of different nature, or to differences in surface 

 on opposite sides, may not the plant cell itself show a difference in 

 permeability in opposite directions, since such a system of double 

 membranes is represented by the cell wall and ectoplast ? 



Rate as related to the concentration of the external solution. 

 Solutions of different osmotic pressures were used as the external 

 solution in order to determine whether or not the rate of water 



table x 



Relation between osmotic pressure applied and 



rate (sodium chloride solution) 



I 

 2 



3 

 4 



5 

 6 



7 

 8 



Number 



ter (in mg.) passing through membrane 

 hour in atmospheres of osmotic pressure 



13-82 



27.65 



22-53 

 21.96 



28.53 



35 37 

 3423 



35 94 



4437 



44.37 

 28.09 



5818 



56.48 



68.93 



41.48 



88.0 



67.89 



66.75 



4279 

 82.15 



102.69 

 88.99 



movement was proportional to the pull applied. Two solutions 

 were used, sodium chloride and cane sugar. The results with 

 sodium chloride are shown in table X. A comparison of the 



