48 MACDOUGAL-hACTION of lipoids in Gi^OWTH. 



with an agar-gelatine plasma filled with a 5 per cent, cane sugar 

 solution gave averages of over 2 c.c. daily when immersed in water,, 

 but action ceased when it was transferred to a 0.005M saponin 

 solution. 



It is evident that the presence of saponin with sugar or salt solu- 

 tions in the contents of the clay thimble or the cell, or in the im- 

 mersion fluid, lessens endosmose, presumably by increasing the per- 

 meability of the membranes, or layers of jelly and the firmer wall. 



Some of the agar (3 parts) -gelatine (2 parts) jelly used in 

 making the plasmatic layer of the cells was dehydrated, coming down 

 to a plate 0.12 mm. in thickness. Trios of section were hydrated 

 under the auxograph with the following increases in thickness at 

 14-16° C: 



Water 2200 per cent. 



Saponin o.oiM 2830 per cent. 



KCl o.oiM 2250 per cent. 



^^^ 1 187s per cent. 



Saponin coiMj 



The actual hydration in the saponin was less than in water, that 

 in KCl was still less, while the combination of the salt and the 

 saponin restrict hydration still more. The action of the saponin on 

 a plasma of the above type would therefore be to lessen permeability 

 alone and in the presence of the salt. This would tend to increase 

 osmotic action, if the plasma alone were concerned. It must be con- 

 cluded, therefore, that the saponin has no action in the artificial cell 

 except that which would lessen permeability of the plasma and 

 increase that of a lipoidal layer and of the porous outer wall. 



Attention was now turned to the more difficult task of interpret- 

 ing the action of living and dried cell-masses in solutions which might 

 theoretically affect the peripheral layer. The measurements of 

 Kahho were taken from roots fully hydrated in distilled water. 

 When such roots were placed in KCl at 0.22M an initial shrinkage 

 of II per cent, ensued within a few minutes, to be followed by an 

 expansion which regained 4 per cent, of the shrunken length. 



The flat joints of Opuntia were chosen as the material for my 

 own tests, as the composition and general behavior of these plants 



