Water Deficit or Unsatisfied Hydration Capacity. 



105 



period of 9 or 10 hours (inclusive of the action of distilled water). 

 The sections then slowly shrunk at rates which would carry them back 

 to original volume in a similar period. The swelling in the balanced 

 solution was equivalent to the effect of its calcium, while the sodium 

 alone gave a greater swelling than the balanced solution. The swell- 

 ing in this salt was as great as in distilled water. 



Sections of young joints of Opuntia have been subjected to a wide 

 variety of tests, and a set of these was placed under conditions similar 

 to those noted for Erigeron. The swelling in distilled water was 7.1 

 per cent, dilute balanced solution 8.7 per cent, sodium chloride 7.2 

 and 8.2 per cent, and in calcium chloride 7.7 and 8.8 per cent. The 

 small differences in the proportionate swelling do not appear to have 

 any bearing on possible antagonisms. 



The masses of tissue used in the above tests were complex as to 

 composition and doubtless already contained some of the salts of the 

 balanced pair. It seemed important to test the effect of antago- 

 nistic salts on a biocolloid inclusive of bean protein, and a simpler one 

 in which agar was combined with glycocoll. The results of the meas- 

 urements were as shown in table 82. 



TABLE 82. 



The amount of imbibition in the balanced solution in both colloids 

 was less than half that in distilled water, and was not much different 

 from that in the sodium chloride. The amount of imbibition in the 

 calcium component used separately was less than that in the sodium 

 chloride alone. No aspect of the above experimentation seems to 

 promise anything of importance concerning the nature of the external 

 layer of the cell, differential action of which to solutions of various 

 kinds is so largely a matter of assumption. In fact, but little of the 

 evidence obtained by the extended experiments described in this 

 volume requires such a conception for its explanation, a conclusion 

 previously set forth very clearly by Kunkel after an experimental 

 examination of some features of the reactions of cells supposedly 

 associated with semi-permeable membranes. 1 



1 Kunkel, Louis Otto. A study of the problem of water absorption. 23d Ann. Report, 

 Missouri Botanical Garden, pp. 26-40. 1912. 



