66 



Hydration and Growth. 



salts in the concentrations in which they occur in the culture solution 

 (table 53). 



The total amount of swelling in the culture solution is scarcely 

 more than half that in distilled water, that in the dipotassic phosphate 

 not falling much below that of water. Swelling in potassium nitrate 

 is much greater than that shown in the culture solution. The low 

 imbibition in calcium nitrate is in accordance with the expectancies. 



Table 53, 



The magnesium salt exercises an imbibitional action equivalent to 

 that of the complete solution. The potassium salts allow a notably 

 greater swelling. Apparently the calcium salt interferes, or exercises 

 an antagonism which results in the averaged total exemplified. The 

 actual relative action of these salts, however, can not be taken up at 

 this time. A consideration of the imbibitional action of the constit- 

 uent salts might yield some data which would be of value in deter- 

 mining the composition of culture solutions for special purposes. 



A similar series of tests of the 

 effect of the nutrient solution Table 54. 



and its components upon grow- 

 ing tissues were made with 

 sections of young stems of 

 Rudbeckia bearing young fiower- 

 heads. Tangential slices were 

 removed from one side to allow 

 expansion and trios of pieces a 

 centimeter long and 3.5 mm. in 

 thickness were placed under the 

 auxographs in a dark room at 



16° C. Air-dried sections of the same stems which had been exposed 

 to the air and light for a day and had shrunk to about half of their 

 original thickness were now placed in identical solutions. The swell- 

 ings of the fresh and of the dried sections are given in table 54. 



