Hydration and Growth of Colloids and Cell-masses. 



119 



nated, except during the few minutes when examinations were being 

 made. The swelling measurements are given in table 96. 



TABLE 96. 



The data given in table 95 yield a number of exceedingly interesting 

 suggestions as to the absorption and incorporation of water by living 

 sections in the presence of various substances. The time in which 

 saturation takes place varies widely in the range of temperatures 

 which is a normal one for this plant. Satisfaction of the water capacity 

 of the sections requires 42 hours at the lowest temperature and but 5 

 hours at the highest in distilled water. The change is from 42 hours 

 to 7 in potassium nitrate and from 32 to 25 in the acidified salt and from 

 20 to 2 in the acid. The living material already contains a normal 

 supply of both substances and immersion in them involves an increase 

 in their action. The action of the sodium hydroxid is, as has been 

 found in many instances, long-continued. The maximum swelling is 

 seen to be accomplished at about 25 C. The general optimum for all 

 of the solutions is, however, probably above this point. 



The initial rate of increase at the highest temperature is great- 

 est, but it is soon checked. Etiolated shoots of the same species of 

 Opuntia were available and the results of the swelling measurements 

 obtained from them afford some interesting comparisons, although 

 it was not possible to run them as nearly parallel as might be wished. 

 These shoots were 18 to 25 cm. long and 1.5 to 2 cm. in width, some of 

 which were hi a chamber at 17 to 19 C. and others in a chamber in 

 which their temperature ranged from 30 to 31 C. Swellings were 

 made at both temperatures, with the results given in table 97. 



The most striking feature of the results is the fact that the material 

 etiolated at the higher temperature shows a more extended and 

 greater swelling at the lower temperature. Unfortunately, the fact 

 that the limiting effects of acidity on imbibition increase with rise hi 

 temperature was not known at the time these tests were carried out. 



If the case of the low-temperature material be taken up, it is seen 

 that its increase is greatest at the high temperature hi water, potas- 

 sium nitrate, acidified potassium nitrate, and acid, while the swelling 

 in alkaline salt and in hydroxid is greatest at the low temperature. 



