3 86 



BOTANICAL GAZETTE 



[may 



that the results obtained indicate that the passage of water through 

 the membrane is analogous to the passage of water through capillary 



tubes. 



previous 



— When the per- 



meability of a membrane is measured at one temperature and the 

 membrane then transferred to another temperature, the question 

 is raised as to whether or not there is any "after effect" of the 



temperature 



determine this uoint m 



fitted into 2 osmometers and a measurement was made of the 

 permeability of each membrane. One osmometer was then placed 

 in a beaker of water in an ice chest at 2.5 C, and the other in an 



1 



oven at 46 C. The next day the two were again placed in the 

 original osmotic solution at the original temperature and readings 

 again taken. The results obtained are given in table VIII. No 

 after effect of a previous temperature, or hysteresis, was observed 

 at the temperatures used in these experiments. 



TABLE VIII 



Intervals of 10 minutes 



25° C. 





First membrane 





First 



27 spaces 

 29 " 



28 " 



29 " 



* 



20 spaces* 



29 " 



29 



Second 



Third 



Fourth 



Fifth 







Second membr; 



First . . 

 Second 

 Third . 

 Fourth 

 Fifth . . 



23 spaces 



23 u 



24 a 



23 spaces f 



24 



22 



23 



a 



* After 14 hours at 2?5 C. 

 t After 15 hours at 45 C. 



Rate as affected by direction of flow of water through membra) 

 A peanut seed coat membrane was placed in an osmometer j 

 measurement made of the rate at which water nassed throu 



from the osmometer 



position 



surface being turned toward the 



