900 
Journal of Agricultural Research 
Vol. XXVIII, No. 9 
4. In the winter considerable variation in sap density is encountered, amounting 
in some cases to complete reversals of the densities of the growing season, due 
to changes in the soluble contents of the plant cells. In the case of evergreen 
shrubs, the conversion of starch to sugars materially increases the density of the 
sap. 
5. A thick leaf having a compact structure with a thick epidermis and cuticle 
tends toward a lower sap concentration through its reduction of water loss from 
the leaf. The presence of epidermal coverings and hairs on the leaves also makes 
for lower sap densities. 
6. Greater sap densities are generally found in the more drought-resistant 
species. 
LITERATURE CITED 
(1) Alter, J. C. 
1919. normal precipitation in Utah. U. S. Dept. Agr. Weather Bur., 
Mo. Weather Rev. 47: 633-636, illus. 
( 2 ) - 
1921. western utah. U. S. Dept. Agr. Weather Bur. Summary Climat. 
Data U. S., Reprint, Sect. 11, 30 p., illus. 
(3) Bates, C. G., Notestein, F. B., and Keplinger, P. 
1914. CLIMATIC CHARACTERISTICS OF FOREST TYPES IN THE CENTRAL ROCKY 
mountains. Proc. Soc. Amer. Foresters 9: 78-94. 
(4) - 
1917. FOREST SUCCESSION IN THE CENTRAL ROCKY MOUNTAINS. Jour. 
Forest. 15: 587-592. 
(5) -and Zon, R. 
1922. RESEARCH METHODS IN THE STUDY OF FOREST ENVIRONMENT. U. S. 
Dept. Agr. Bui. 1059, 209 p., illus. 
(6) Beckmann, E. 
1888. UEBER DIE METHODE DER MOLEKULARGEWICHTSBESTIMMUNG DURCH 
gefrierpunktserniedrigung. Ztschr. Phys. Chem. 2: 638-645. 
(7) Bose, J. C. 
1918. life movements in plants. Trans. Bose Research Inst., v. 1, 
251 p., illus. 
(8) Bouyoucos, G. J., and McCool, M. M. 
1915. THE freezing-point method as a new means of MEASURING THE 
CONCENTRATION OT THE SOIL SOLUTION DIRECTLY IN THE SOIL. 
Mich. Agr. Exp. Sta. Tech. Bui. 24, 44 p., illus. 
(9) - 
1916. FURTHER STUDIES ON THE FREEZING POINT LOWERING OF SOILS. 
Mich. Agr. Exp. Sta. Tech. Bui. 31, 51 p.., illus. 
( 10 ) - 
1916. THE FREEZING-POINT METHOD AS A NEW MEANS OF DETERMINING 
THE NATURE OF ACIDITY AND LIME REQUIREMENT OF SOILS. Mich. 
Agr. Exp. Sta. Tech. Bui. 27, 56 p., illus. 
at)- 
1917. CLASSIFICATION AND MEASUREMENT OF THE DIFFERENT FORMS OF 
WATER IN THE SOIL BY MEANS OF THE DILATOMETER METHOD. 
Mich. Agr. Exp. Sta. Tech. Bui. 36, 48 p., illus. 
(12) -and Laudeman, W. A. 
1917. THE FREEZING-POINT METHOD AS A NEW MEANS OF STUDYING VELO¬ 
CITY OF REACTION BETWEEN SOILS AND CHEMICAL AGENTS AND 
behavior of equilibrium. Mich. Agr. Exp. Sta. Tech. Bui. 
37, 32 p. 
