THE OSMOTIC CONCENTRATION AND ELECTRICAL 



CONDUCTIVITY OF THE TISSUE FLUIDS OF 



LIGNEOUS AND HERBACEOUS 



PLANTS 1 



BY J. ARTHUR HARRIS, ROSS A1KEN GORTNER AND JOHN V. 



LAWRENCE 



I. The Osmotic Concentration of the Leaf Tissue Fluids of 

 Herbaceous and Ligneous Plants 



An examination of earlier literature on the osmotic con 

 centration of plant tissue fluids shows various suggestions of a 

 difference in the osmotic concentration of the leaf fluids of 

 herbaceous and ligneous plants. As early as 1911 Fitting 2 

 noted from his plasmolytic studies on desert plants that the 

 lowest osmotic pressures are found in annuals and the highest 

 in shrubs. 



The existence of a differentiation of ligneous and her 

 baceous plants with respect to the magnitude of the osmotic 

 concentration of their tissue fluids was first demonstrated in 

 a strictly quantitative manner by work on the sap of the plants 

 of the spring flora of the Arizona deserts 3 in the neighborhood 

 of the Desert Botanical Laboratory. Because of the strongly 

 contrasted environmental conditions in these southwestern 

 deserts the growth forms are sharply differentiated. Follow 

 ing as closely as possible Thornber s classification of the 

 growth forms, 4 thereby obviating any possible question of 

 personal equation in the classification of the plants, we find 

 the results for freezing point lowering given in Table I. 5 



1 Studies carried out by the co-operation of the Department of Experi 

 mental Evolution and the Department of Botanical Research of the Carnegie 

 Institution of Washington. 



2 H. Fitting: Zeit. Bot., 3, 209-275 (1911). 



3 J. Arthur Harris, J. V. Lawrence and R. A. Gortner: Phys. Res., 2, 

 1-49 (1916). 



4 J. J. Thornber: Pub. Carnegie Inst. Wash., No. 113, pp. 103-112 

 (1909). 



6 Harris, Lawrence and Gortner: Loc. cit., pp. 45-46. The averages 

 in the table are averages of species determinations, not of species means. 



