2S MACDOUGAL— ACTION OF BASES AND SALTS 



The hydration capacity of the roots grown in saHne soil was less 

 throughout than that of the roots grown in sand in which the salts 

 introduced by the water of irrigation were much attenuated. Other 

 differences suggest that the roots in the saline soli were more highly 

 proteinaceous and also had a higher incorporated salt content. 



Still another test was made with sections taken from the joints 

 of Opuntia growing near the Desert Laboratory in February, 1921. 

 The course of change in the chemical composition of this material 

 is known in some detail. The pentosan constituent of the cell- 

 colloids reaches a maximum earlier in the winter and was lessening 

 at the time of the experiments but would still be so large as to make 

 for a dominantly pentosan colloid. Swellings as in Table XIII were 

 exhibited by two samples which are given in separate columns. 



TABLE XIIL 



Water 164 168 



KOH o.oiiV 177 17s 



KOH o.ooiAT 152 158 



KOH o.oooi# 169 153 



HCl o.oiA'^ 146 136 



HCl o.ooiN 172 161 



HCl o.oooiA^ 150 150 



KCl o.oiM ISO 153 



KCl o.ooiM 146 



KCI o.ocx)iM 179 



Swellings greater than in water are induced by KOH with a PH 

 value of 12, in KCl with a PH value of 5.7 and by HCl at o.ooi A'' 

 with a PH value of 5.7. 



Here as in all tests of living material the measurements are com- 

 plicated by osmotic effects, although it is to be noted that the final 

 swellings in Opuntia are reached after immersion for a day and the 

 results are more clearly imbibitional than in any of the other ma- 

 terial used. 



General Considerations. 



The following generalizations may be made upon the basis of 

 the experimental results described in the foregoing paper. 



I. The strong metallic bases which were found to lessen the 

 swelling of agar to a degree corresponding to their relative posi- 



