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CARNEGIE INSTITUTION OF WASHINGTON. 



and growth of acid cell-masses. The petioles of some young plants of 

 a Solarium hybrid in the glass house at Tuscon were available on April 

 21, 1918. Trios of sections were placed in distilled water and acids 

 at 18° to 38° C, with results as follows: 



The swelling in distilled water was nearly three times as great at 

 the higher temperature, while in the acid solution a retardation took 

 place which limited the total at the higher temperature to something 

 over a half that possible at the lower point. The total swelhng in 

 acid at the lower temperature occupied an hour and at the higher 

 temperature it was a matter of 10 or 15 minutes. A similar speeding- 

 up of imbibition in water was observed. The total capacity at the 

 lower temperature was not reached for 8 or 10 hours, while at the 

 higher it was something under 2 hours. 



A second test of variations in temperature upon material in an 

 acidified condition was made with dried sections of Opuntia 0.43 to 

 0.46 mm. in thickness, which gave the following: 



The increase in swelhng in distilled water is seen to be about twice 

 that in the acid in the rise from 18° C. to 38° C. The influence which 

 the condition in question may exert on the rate of growth is obvious. 

 Thus the course of enlargement of an organ or of a cell-mass, in so 

 far as this consists in hydration, may vary widely in the first instance 

 because of the residual acids in the colloids, and the balance or accum- 

 ulation of this will in turn depend upon the effect of the enzymatic 

 or respiratory process in metabolism. A rise of 10° from the customary 

 morning temperature of 15° C, which has been encountered in so 

 many of these experiments, would result in an acceleration of growth 

 largelj^ determined by the state of acidosis of the plant. A rise from 

 the same temperature later in the day or under other conditions of 

 illumination would necessarily have a different result. 



