64 CARNEGIE INSTITUTION OF WASHINGTON. 



The deductions to be drawn from these figures, all being averages 

 of 3 to 9 measurements, are numerous, but attention must be confined 

 to a few pertinent cases. 



(1) It is to be seen that equimolecular concentrations of the three 

 organic acids present small divergence of effect on agar and more 

 positive differences in agar-protein. 



(2) Agar swells more in succinic acid than in its amino-compound, 

 but reverses this relation notably in the acetic-glycocoll couple. 



(3) The agar-protein biocolloid shows notably greater hydration 

 in the amino-acids than in the related organic acids, and greater even 

 than the hydration in distilled water. 



(4) Equimolecular concentrations of amino-acids produce notably 

 greater swellings of the biocoUoids in comparison with related organic 

 acids implying the positive action of factors other than the hydrogen- 

 ion concentration. 



(5) Glycocoll facilitates hydration in all concentrations above 0.01 

 M. in both agar and agar-proteins, and also in agar-gelatine, the data 

 of which are not given in this paper. This fact goes far in explanation 

 of the scattered results obtained by various workers, in which accel- 

 erated growth or increased total growth has been seen to result from 

 the addition of glycocoll to nutrient solutions. Such increases have 

 been attrituted to catalytic action by Dakin and others. 



(6) The amine, asparagin, induces a maximum hydration, greater 

 even than that possible in agar in distilled water, and very high at all 

 concentrations. Similar action was exerted on agar-gelatine and agar- 

 protein plates. The positive action of both glycocoll and asparagin 

 is indicated by the fact that the maximum effect is reached at certain 

 concentrations above the minimum concentration. 



The Solution and Fixation accompanying Swelling and Drying of BiocoUoids 

 and Plant Tissues, by D. T. MacDougal and H. A. Spoehr. 



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

 biocolloid, a dried plant-section, or a mass of living protoplasts, 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 com- 

 pounds present. These diffusions encounter highly specialized condi- 

 tions 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 cellu- 

 lose-pectose walls inclosing the cells. 



In the course of some work on the imbibition and growth of plants, 

 the analyses of which show that the water relation of the protoplasm 

 is determined by the pentosan-protein proportion, and that the activ- 



