July i, 1921 
Pathogenicity of Corticinm vagum on the Potato 
481 
(8) The degree of growing-point destruction appeared as an important 
factor in determining the increase or the decrease from the normal of the 
number of stems above the soil in an infected area. 
(9) No “critical temperature" for the pathogenicity of the fungus on 
the potato appeared at the lower range of temperature used. 
(10) The temperature requirements of the potato plant were found to 
vary with its different stages of growth. The young sprouts, while in 
the soil, grew most rapidly at 24 0 C. Growth was greatly retarded at 15 0 
and below. At soil temperatures above 24 0 the plant exhibited such 
abnormal responses as excess branching, shortening of the internodes, 
decreases in segmentation of the leaves, and decrease of the diameter of 
the stems. A soil temperature of approximately 18 0 proved optimum 
for the later and continued development of the potato plant. 
(11) The soil temperature of 18°C. found most favorable for the patho¬ 
genic action of Corticinm vagum approximates closely the temperature of 
the soil optimum for the general development of the host. 
(12) Soil temperature data obtained from field studies with the potato 
and from greenhouse experiments with the pea and the bean will be pub¬ 
lished in a later paper. 
LITERATURE CITED 
(1) Balls, W. Lawrence. 
1906-7. Tins physiology of a simple parasite. In Yearbook Kliediv. Agr. 
Soc. 1905, p. 171-195, pi. 6-7; 1906, p. 91-m, pi. 13-16, plan. 
References, 1905, p. 194. 
(2) - 
1908. temperature and growth. In Ann. Bot., v. 22, no. 88, p. 557—591, 
4 fig* 
(3) Edson, H. A., and Shapovalov, M. 
1918. potato-stem lesions. In Jour. Agr. Research., v. 14, no. 5, p. 213-220, 
pi. 24-26. 
(4) Gilman, J. C. 
1914. THE RELATION OP TEMPERARURE TO THE INPECTION OP CABBAGE BY 
Fusarium congluTinans, wollEnw. (Abstract), in Phytopathology, 
v. 4, no. 6, p. 404. 
(5) Johnson, James, and Hartman, R. E. 
1919. INFLUENCE OP SOIL ENVIRONMENT ON THE ROOTROT OP TOBACCO. In 
Jour. Agr. Research, v. 17, no. 2, p. 41-86, 2 fig., pi. 1-8. Literature 
cited, p. 85-86. 
(6) Jones, L. R. 
1917. SOIL TEMPERATURES AS A FACTOR IN PHYTOPATHOLOGY. Ill Plant World, 
v. 20, no. 8, p. 229-237, 2 fig. Literature cited, p. 236-237. 
(7) Livingston, Burton Edward. 
1908. a method for controlling plant moisture. In Plant World, v. 11, 
no. 2, p. 39-40. 
(8) Morse, W. J., and Shapovalov, M. 
1914. THE rhizoctonia disease op potatoes. Maine Agr. Exp. Sta. Bui. 230, 
p. 193-216, [ 11] pi. Literature cited, p. 216. 
(9) Orton, W. A. 
1913. environmental influence in the pathology op solanum tuberosum. 
In Wash. Acad. Sci. Jour., v. 3, no. 7, p. 180-190, 3 fig. 
