152 Hydration and Growth. 



sections were therefore taken at l''30° p. m., when the plant stood at a 

 temperature of 22° C, and these were swelled in the dark room at 

 once with solutions which stood at 18° to 20° C. during the time of the 

 swelling. The increases were as follows: 



Table 113. 



p. d. 



Distilled water 70 



Citric acid, 0.01 N 19 



Sodium hydroxid, 0.01 M 46 



Potassium chloride, hydrochloric acid, O.OI M 14 



The examination of the sections after the records were complete 

 showed that they were variously twisted and curled, due to the fact 

 that the internal parenchymatous tissues had swelled more than the 

 external layers. So far as could be estimated by simple observation 

 without measurement, the error did not double the measurement, how- 

 ever. Consequently it is to be seen that the imbibition capacity of 

 these stems, due to a depletion of the water-balance, is much greater at 

 noon than in early morning. 



A repetition of the first test with whole sections that could not so 

 readily twist showed that another series of sections taken at 8 a. m. 

 sweUed as foUows, at 18° to 20° C: 



Table 114. 



p. ct. 



Distilled water 4 



Citric acid, 0.01 N 4 



Sodium hydroxid, 0.01 M 6.5 



Potassium chloride, hydrochloric acid, 0.01 M 6 



This series was characterized by the satisfaction of the full hydration 

 capacity withia an hour or two, except in the case of the alkaline solu- 

 tion, in which the increase was very gradual. The material had re- 

 turned to its original dimensions within 6 hours in the other liquids 

 and continued to shrink. This action, coupled with decoloration, was 

 especially marked in the acidified saline solution. As a still further 

 verification of the above results, a trio of sections exactly like those of 

 the above series were taken at midday on the following day, and these 

 swelled 14 per cent in water, while another trio increased 10 per cent in 

 the acidified saline solution before shrinking. 



The earUer measurements of the swelling of the sunflower having 

 been made with the terminal intemodes of growing stems, a final series 

 was made in which were used the cotyledonary stalks from which the 

 plumules had been cut a day or two earlier. Measurements as follows 

 were obtained at 17° to 19° C. 



Table 115. 



p. d. 



Distilled water 6 



Citric acid, 0.01 N 4 



Sodium hydroxid, 0.01 M 7 



Potassium chloride, hydrochloric acid, 0.01 M 7 



