MacDOUGAL— HYDRATION AND GROWTH. 355 



A preparation was now made in which two parts of the water 

 sohible protein from oats was added to 8 parts of agar in a 2.5 per 

 cent, solution of the latter. The plates dried to a thickness of .25 

 mm. When sections of such biocoUoids were swelled in the gly- 

 cocoll series, the results were as shown in the table, the hydrations 

 in concentrations less than o.oi M approaching and surpassing those 

 in distilled water. 



The action of acids being supposedly due to the hydrogen ion 

 concentration, a test was made of the action of a solution in which 

 glycocoll (amino-acetic) was added to acetic acid. Trios of surface 

 slices of Opuntia which had dried to a thickness of 0.8 mm. swelled 

 163 per cent, in .05 A'' acetic acid and 156 per cent, in a .05 A^ solu- 

 tion of acetic acid and glycocoll. No especial significance can be 

 attached to the lesser swelling in the double solution, except that no 

 evidence as to acceleration of swelling by the addition of the amino- 

 acid was obtained. 



Next trios of sections of 8 parts agar and 2 parts gelatine 0.3 

 mm. in thickness were swelled in the acetic and amino-acetic solu- 

 tions 0.01 A^ at 18° C. The swelling in the acetic acid alone was 

 1450 per cent., while that in the combined solutions was but 1300 

 per cent., which agreed with the previous efifects in being less than 

 in the acid alone. 



Trios of sections of agar swelled 1875 per cent, in a o.oi A^ solu- 

 tion of acetic acid at 18° C, while a combined solution of equiva- 

 lent molecular concentration showed a swelling of 1750 per cent. 



There now remained the test with Hving tissues. Some joints of 

 Opuntia blakeana of 1918 which had been brought from Tucson two 

 months earlier and had laid on the table with the result that they had 

 lost much water but were still alive, were used for this test. A trio 

 of sections with an average thickness of 6 mm. swelled 60 per cent, 

 in the hundredth normal acetic acid, while a similar trio which meas- 

 ured 5.5 mm. on the average swelled but 45.5 per cent, in the com- 

 bined acetic-glycocoU solution. A second feature distinguished the 

 two reactions, the swelling in the acetic being continuous and ap- 

 proaching zero during the 20 hours of measurement, while in the 

 combined solution full expansion was reached in 4 hours after which 

 a shrinkage resulted in a loss of nearly 5 per cent. 



