214 Journal of Agricultural Research voi. xiv, no . s 
from a given lesion. In the spring of 1918 several specimens were 
obtained from Florida, some of wliich had characteristic brown lesions on 
the stems. Plantings made from these diseased areas yielded pure 
cultures of F. oxysporum. Identical results were also obtained with 
some of the material collected recently in the vicinity of the District of 
Columbia. 
INOCULATIONS 
Although certain preliminary tests were made in the field, this work 
was carried on chiefly under greenhouse conditions at Washington, 
D. C., with disinfected seed and steam-sterilized soil and pots, watered 
from the city mains supplied with clarified and filtered Potomac River 
water. The following method of inoculation has been found very 
satisfactory: When the young plants were about 2 or 3 inches high, the 
soil was removed at one side of the plant clear down to the seed piece 
(on the average, about 2 inches from the surface of the soil), care being 
taken to avoid as much as possible any injury to the epidermis of the 
stem. Then the culture was removed from the test tube on a piece of 
clean absorbent cotton, and the preparation was placed on the exposed 
side of the stem. Each fungus had been grown for this purpose on 
three kinds of medium; rice, cooked potato cylinders, and melilotus 
stems. Finally the soil was replaced and heaped up about the plant, 
nearly covering it. Control plants were treated in a similar way except 
that sterile culture medium instead of fungus cultures was applied to 
the stems. About four weeks after inoculation the plants were care¬ 
fully dug, washed, and examined. Besides the fungi isolated from the 
potato, a number of Rhizoctonia strains 1 from various other hosts, as 
well as authentic cultures of several species of Fusarium, were included 
in the tests. The combined detailed results of these experiments are 
given in Table I. 
Tabi^S I .—Results of the potato-stem inoculations with Rhizoctonia solani, Fusarium 
spp. t and several other fungi 
Name of culture. 
Date of isolation. 
Num¬ 
ber of 
plants 
inocu¬ 
lated. 
Num¬ 
ber of 
plants 
in¬ 
fected. 
Character of injury produced. 
Rhizoctonia solani (R. po- 
tomacensis Wollenw. 
from tomato). 
August, 1912... 
S 
S 
Irregular, deep, dark-brown 
lesions on stems; stolons 
and new tubers also af¬ 
fected. 
R . solani, R. Kan. (from 
beets). 
1913 . 
5 
3 
Brown discoloration at the 
base of the stems. 
R. solani, R. S. (from 
beet seedlings). 
July, 1912. 
5 
3 
Large brown canker in one 
case and a slight russet- 
ting in two others. 
, 1 The word “strain” m its application to Rhizoctonia is used in the present paper merely to differen¬ 
tiate cultures obtained from different hosts or from the same host from different localities. It does not 
imply any reference to their taxonomic relationships. 
