THE SOLUTION AND FIXATION ACCOMPANYING 

 SWELLING AND DRYING OF BIOCOLLOIDS A 



AND PLANT TISSUES /4J 



La, 



D. T. MacDOUGAL and H. A. SPOEHR 



Desert Laboratory, Tucson, Arizona 



J* 



The hydration of a colloidal mass whether it be a dried plate 

 of a biocolloid, a dried plant section or a mass of living pro- 

 toplasts is all but invariably accompanied by the solution or 

 extraction of some of the substances of the colloidal mass. The 

 material found in such extracts will in all cases be determined 

 by the diffusibility of the compounds present. These diffusions 

 encounter highly specialized conditions at the external limits of 

 the protoplasts where a colloidal phase boundary separates the 

 elastic gels and highly viscid emulsoids of the pentosan-protein- 

 lipoid protoplasm from the denser more rigid cellulose-pectose 

 walls enclosing the cells. 



Attempts to fix upon the composition of the "semi-per- 

 meable" membrane constituted by this important phase bound- 

 ary have naturally failed, since it is by its very nature unstable, 

 and since it must in every case be the product of the two col- 

 loidal masses which come together and the material which comes 

 to the surfaces of the impinging colloidal masses will be de- 

 termined largely by the character of the protoplasm and of the. 

 wall. 1 Such conditions offer fruitful conditions for unprofitable 

 controversies, which it is not proposed to review at this time. 



Measurements and analyses of the chemical nature and con- 

 centration of compounds which will cause the disruption and 

 displacement of the wall-protoplasm boundary in "true" and 



1 Free, E. E. A colloidal theory of permeability. Plant World, 21: 141. 

 1918, and Wodehouse, R. P. Direct determinations of permeability. Jour. 

 Biol. Chem. 29:453. 1917. 



129 



THE PLANT WORLD, VOL. 22, NO. 5, 

 MAY, 1919 



