60 CARNEGIE INSTITUTION OF WASHINGTON. 



axis of deposition of material was in the vertical, and the swelhng in 

 this direction would of course be correspondingly in excess of that 

 in the plane of the sections. It is extremely unlikely that any of the 

 colloidal masses of the cell are isotropic as to deposition or structure 

 and the use of thin plates seemed a feature which might increase the 

 similarity of behavior with that of the plant. The strands, sheets, or 

 masses of material in the cell are of course mostly thinner than the 

 plates used in the experiments, which, however, would affect speed of 

 imbibition more than the total amount. 



Trios of sections of sheets of the dried colloids 2 mm. to 4 mm. by 

 3 mm. to 6 mm. were placed in the bottom of Stender dishes or of heavy 

 watch-glasses securely seated on iron cylinders. Triangles of glass 

 were placed on the sections, and the vertical arms of auxographs were 

 rested in a socket in the center of the triangles. Any change in thick- 

 ness of the sections would be registered immediately. 



The systematic endeavor to construct a colloidal mixture which 

 would display some of the fundamental physical properties of proto- 

 plasm of plants has resulted in finding that a mixture of substances of 

 two of the three more important groups of constituents, carbohydrates 

 and proteins, shows the imbibitional behavior of tissues and tracts of 

 protoplasts of the plant. The differential action of such biocolloids 

 in solutions yields many striking parallels with growth. The general 

 identity of constitution of these colloidal mixtures and of cell-masses, 

 and the obvious similarity of their behavior, make it possible to cor- 

 relate more closely the processes of imbibition, metabolism, and growth, 

 and on the bases of their interrelation to interpret growth enlargement 

 and incidental variations in volume and size of organs. 



It is also to be suggested that the differential action which might 

 ensue from the addition or subtraction of a nitrogenous compound from 

 the carbohydrate body of protoplasts in special tracts, changing the 

 imbibition capacity of chromosomes, of spindles or cell-plates, etc., 

 may well play an important part in the mechanics of mitosis and cell- 

 division. 



Imhihition in Biocolloids as affected hy Acidosis, Alkalosis, and Neutralization, 



by D. T. MacDougal. 



Some systematic information as to the swelling of agar and gelatine 

 in water, acids, alkaUes, and salts with regard to concentration of the 

 reagents is available as the result of work in the physics of simple col- 

 loids. The reactions of sections of Uving plants to similar solutions 

 demonstrated that protoplasm shows a characteristic behavior which 

 may be simulated fairly well by a mixture consisting of a base of an 

 inert carbohydrate like agar and albumen or its derivatives, which for 

 convenience has been designated as a biocolloid. The swelhng of dried 

 sections of biocolloids gives data which can not be anticipated by a con- 



