MACDOUGAL-^ACTION OF LIPOIDS IN GROWTH. 35 



erated by KCl in living cell-masses of Opuntia. This result is not 

 in agreement with Boas, who found that the salt accelerated the action 

 of saponin upon cells of Tradescantia. 



9. The hydration of such living cell-masses is not definitely af- 

 fected by variations in acidity up to PH 2. No positive increases 

 were noted in KHO in weaker concentrations, but swelling was les- 

 sened in o.oiN. 



10. Dried cell-masses display a minimum effect from saponin at 

 about the same concentration as the living material, but the, swelling 

 which is maintained increases with the concentration to about 0.005M. 



11. The hydration of dead cell-masses was not definitely affected 

 by HCl at o.oiN, but at weaker concentrations, o.ooi to 0.0002A'', the 

 swelling was greater than in water. After the neutral point is passed 

 some increase is to be noted in KHO o.ooiN, which reaches its maxi- 

 mum at o.oiN. 



12. The hydration reactions of dead cell-masses of Opuntia in 

 acidified solutions are those which might be displayed by a biocolloid 

 in which the protein and pentosan components were nearly equal in 

 quantity. The hydration reactions of living cell-masses are such that 

 permeability is increased and swelling lessened in hydroxide at o.oiN 

 and o.oo5A^. This reaction, like that of saponin, is reversed in the 

 dead cell-masses in which swelling increases with the concentration. 



Cytologists have for the most part considered the so-called plas- 

 matic membrane as a peripheral layer not separable from the cyto- 

 plasm and by implication to consist of proteins. Seifriz regards this 

 suppositious membrane as a highly viscous layer about i /a in thick- 

 ness.^ In the recent notable contribution by Hansteen-Cranner the 

 peripheral layer of plasmatic substance is regarded as lipoidal, con- 

 sisting of a disperse phase of hydratable material not soluble in water, 

 in a continuous phase of water-soluble lipoid. This formation is con- 

 tinuous with a fundamental lipoid meshwork of the plasma. A 

 lipoid meshwork from the peripheral layer is also supposed to extend 

 through or into the cell-walls. The conclusions thus briefly noted 

 are held to sustain the general contention of Overton as to the lipoidal 



2 Seifriz, W., " Observations on Some Physical Properties of Protoplasm 

 by Aid of Microdissection," Annals of Bot., 35 : 269-296, 1921. 



