66 CARNEGIE INSTITUTION OF WASHINGTON. 



Imhihition of Gelatine and Agar Gels in Solutions of Sucrose and Dextrose, 



by E. E. Free. 



It has been shown by MacDougal that a biocolloid consisting chiefly 

 of agar and a small proportion of some nitrogenous substance exhibits 

 the principal water-relations of living plants. The experiments on this 

 subject have dealt chiefly with the effects of salts, alkalies, and acids 

 upon the swelling of these colloids and of living material. All the v/ork 

 upon this subject has had for its chief purpose the simulation of con- 

 ditions in the plant-cell in which sugars are almost universally present. 

 Much has been written concerning their osmotic action. A compre- 

 hensive series of swelling tests was made with sucrose and dextrose 

 under properly guarded conditions upon the swelling of biocolloids con- 

 sisting of varying proportions of agar and gelatine. 



For the sugar solutions having concentrations less than 25 per cent, 

 the results do not differ from those for distilled water more than is 

 explainable by the accidental variation normal to the method when 

 the temperature is not controlled precisely. The effects of N/100 

 acid and alkah found bj' jNlacDougal were many times the variations 

 here observed, and one may conclude that neither sucrose nor dextrose, 

 in concentrations under 25 per cent, has any important effect on the 

 swelling of gelatine-agar gels in water — important, that is, in com- 

 parison with the effects of acids or alkalies. With sugar concentrations 

 of 50 per cent the data show a markedly lessened swelling of all the 

 gels in sucrose and of the two low-gelatine gels in dextrose. It maj' be 

 that the two high-gelatine gels also swell less in 50 per cent dextrose, 

 but the decrease is not certainly determinable from the single test which 

 was made. This decrease in swelling in concentrated sugar solutions 

 is to be expected from analogy with the osmotic behavior of such solu- 

 tions and does not indicate any specific effect of sugar, either on the 

 swelling or imbibition capacity of the gels themselves. 



The Transpiring Power of Plants, by Edith B. Shreve. 



Recent improvements in the method for determining the index of 

 transpiring power of plants by means of cobalt-chloride imper ha^'e 

 resulted in the use of the method by several investigators in different 

 parts of the United States.^ Since these workers are using the tripar- 

 tite slips made from standardized paper which was manufactm-ed in 

 Dr. Livingston's laboratory in Baltimore, it is hoped that their results 

 will be comparable and that they will lead toward a more exact knowl- 

 edge of the transpiring power of various plants under many environ- 

 mental conditions. The method is also being used to determine the 

 drought-resistant qualities of dift^erent strains of economic plants. 



^Livingston, B. E., and E. B. Shreve. Improvements in the method for determining the 

 transpiring pov.er of plant surfaces by hygrometric paper. 



