RELATION OF CERTAIN SOIL FACTORS TO THE IN¬ 
FECTION OF OATS BY LOOSE SMUT* 
By LuctlliE K. Bartholomew, formerly Assistant Pathologist, and Edith Seymour 
Jones, formerly Scientific Assistant, Office of Cereal Investigations, Bureau of 
Plant Industry, U. S. Department of Agriculture * 
INTRODUCTION 
In order to interpret properly the results obtained by experimenting 
with a disease, it is desirable to understand the effect of similar con¬ 
ditions upon the host and fungus apart from each other as well as in 
combination. Accordingly, an attempt has been made in the present 
paper to analyze the effects of certain soil factors, first upon the fungus, 
Ustilago avenae (Pers.) Jens., and upon the host, Avena nuda E., and 
then upon the two in combination. 
The literature relative to the problem in hand has been adequately 
reviewed in a related publication^ by the junior author of this paper 
(in this issue of the Journal of Agricultural Research), so no further 
detailed consideration of that feature will be attempted in this paper. 
CONDITIONS OF THE EXPERIMENTATION 
There are certain environmental factors y^hich must be g^ven thorough 
consideration in any well-balanced series of pathological investigations. 
Their relative importance may vary with the host and the fungus under 
consideration, but their stmidardization and control, in so far as these 
are possible, are imperative. Probably the four most important of 
these factors involved in the present investigatioj^ are t^peratme, 
moisture, composition of the medium, and its acidic or basic reaction. 
The temperatures were regulated v^y satisf^torily by the use of 
temperature tanks.** Hie soil moistures were computed ^d maintained 
in terms of the saturation point of the soil, which w^ determined by the 
commonly accepted standard methods, ihe soil was sifted through wire 
gmze into standard i-centimeter cups, which wer^ leveled off by means 
of a spatula without tamping, and then were set into a dish of water of 
known temperature mA alloiyed to stand until the soil was thoroughly 
saturated. The cups then were removed, drained until no more water 
dripped from the under surface, ^nA weighed. The soil was dried at a 
temperature of loo to i lo® C until it reached a constanf^ weight. From 
these data the water-holding capacity of the soil w^ calculated. The 
standardization of soil water on the basis of dry weight, e. g., lo gm. of 
1 Accepted for publication Aufif. 21, 1922. . . , ^ 
• The research herein recorded was conducted under the direction of Dr. G^rge ]VI. Reed, formerly 
pathologist in charge of cereal smut investigations. Bureau of Plant Ipdiistry, Washington, D. C., but 
now at the Brooklyn Botanic Gardens. We wish to extend our grateful thanks to him as well as to 
Dr. L. R. Jones and his associates in the Department of Plant Pathology, University of Wisconsin, for 
their hearty cooperation at all times. . , it 
This paper presents the results of investigations conducted cooperatively by the Office 01 Cereal Investi¬ 
gations, Bureau of Plant Industry, and the Department of Plant Pathology of the Wisconsin Agricultural 
Experiment Station. 
»JoNBs, Edith Seymour. influbncB op temperature, moisture, and oxygen on spore germina¬ 
tion OP USTILAGO avenae. In Jour. Agr. Research, v. 24, p. S77-S9i. 3 fig. Literature dted, p. 590 -S 9 i. 
• < Jones, L. R. soil temperatures as a pactor in phytopathology. In Plant World, v. 20, p. 229-237. 
1917. Literature cited, p. 236-237. 
Journal of Agriculture Research, 
Washington, D. C. 
aec 
(S69) 
Vol.XXIV.No., 
May 19, 1923 
Key No. G-30X 
39364—23-3 
