160 Hydration and Growth. 



2.8 mm. to 3 mm., is shown by the measurements of swellings, made 

 at 15° to 16° C, shown m table 118. 



Table 118. 



p. ct. 



Distilled water 8.2 



Citric acid, 0.01 N 5.4 



Potassium hydroxid, 0.01 M 12.5 



Potassium nitrate, 0.01 M; citric acid, 0.01 N 8.2 



Actually lessened imbibition took place in acid as compared with that 

 in water; the addition of equimolecular solution of potassium nitrate 

 to acid brought the swelling up to that in water. The total absorbed 

 in alkaU was markedly greater than in any solution tested. 



The measurements of variations in length and thickness of the suc- 

 culent leaves of Mesembryanthemum, stems of Helianthus, and of the 

 pods of Phaseolus, and the flattened stems of Opuntia, yield ample 

 evidence that the fluctuations in growth show a direct relation to the 

 hydration capacity of the growing cell-masses, and that as a morpho- 

 logically complex member or organ approaches maturity, the fully 

 developed tissues show a varying water capacity different in many 

 respects from that of the embryonic cell-masses. Some of the irreg- 

 ularities in the course of growth of internodes are due to the fact 

 that these members include regions of embryonic tissue and tracts in 

 all stages of differentiation approaching maturity. 



