304 BOTANICAL GAZETTE [october 



Summary 



The expressed sap from barley plants grown in water, sand, 

 and soil cultures under controlled conditions has been examined 

 with the following results: 



1. The osmotic pressures in the sand and water cultures are 

 reflected in the cell sap of the tops and roots. 



2. The electrical conductivity of the nutrient solution has a 

 marked influence on the conductivity of the sap. This is as 

 marked for the tops as for the roots. The conductivity of the 

 plant sap is from 4 to 50 times greater than that of the nutrient 

 solution. 



3. The sap from the tops of all plants grown in sand and soil 

 cultures or water cultures of different concentrations and reactions 

 had almost the same Pjj value, approximately 6.0. 



4. Samples of sap from plants grown on 6 different soils under 

 the same cHmatic conditions were analyzed for importa^nt ele- 

 ments. In every case the concentration in the sap was found to 

 be very much greater than in the soil solution. 



5. The d}Tiamic nature of the relation between the soil solution * 

 and the plant is emphasized. 



Division of Agricultural Chemistry 



California Agricultural Experiment Station 



Berkeley, Cal. 



LITERATURE CITED 



1. Atkins, W. R. G., Recent researches in plant physiology. London. 1916. 



2. BouYOUCOS, G. J., and McCool, M. M., The freezing point method as a 

 new means of measuring the concentration of the soil solution directly in 

 the soil. Mich. Agric. Exp. Sta. Technical Bull. no. 24. pp. 1-44. 1915. 



3. Haas, A. R., The acidity of plant cells as shown in natural indicators. 

 Jour. Biol. Chem. 27:233-241. 1916. •« 



4. McCooL, M. M., and Millar, C. E., The water content of the soil and 

 the composition and concentration of the soil solution as indicated by 

 the freezing point lowerings of the roots and tops of plants. Soil Science 

 3:113-138. 1917. 



5. Sharp, L. T., and Hoagland, D. R., Acidity and absorption as measured 

 by the hydrogen electrode. Jour. Agric. Research 7:123-145. 1916. 



6. Stewart, G. R., Effect of season and crop growth in modifying the soil 

 extract. Jour. Agric. Research 12:311-368. 1918. 



7. Truog, E., Soil acidity. Its relation to the growth of plants. Soil Science 

 5:169-195. 1918. 



