196 
Journal of Agricultural Research 
Vol. V, No. s 
Falls, N. Y.; Potomac Flats, Washington, D. C.; Arlington, Va.; etc. 
It enters the stem end of the tubers most commonly, but also invades 
lenticels and wounds. In some cases the affected tissue is light colored 
and soft, suggesting bacterial rot—i. e., practically the jelly-end rot. 
More often in the East it is characterized externally by a firm sunken 
area with the underlying parenchyma brown to black, dry, tough, and 
sharply differentiated from the healthy tissue. 
This stem-end wound and lenticel dry-rot caused by F. radicicola may 
be regarded as a form of jelly-end rot. The organism is one of the causes 
of jelly-end rot, but the field and storage conditions where it occurs are 
different. Under conditions of high humidity the rot is of the jelly-end 
type; where the humidity or temperature is low and the action of the 
fungus less rapid, dry-rot develops, the affected tissue being more firm 
and darker colored as a result of drying and oxidation. (See p. 197, 
PI. XV, fig. 4, 5.) Both types occur in California, Oregon, and Idaho, 
sections under irrigation. The dry-rot phase was the one most fre¬ 
quently submitted for diagnosis from other localities—i. e., of presumably 
slower development at lower temperatures. 
INOCULATION 03 ? POTATO TUBERS WITH FUSARIUM RADICICOLA 
F. radicicola 2842; isolated in October, 1913, from jelly-end rot of 
Burbank potato from Middle River, Cal. Unfortunately, the number 
of tubers in the experiment with this strain was not recorded. About 
1 peck of potatoes of the Burbank variety and K peck of the Netted Gem 
variety were used for inoculation and controls. The tubers were incu¬ 
bated at temperatures ranging from 14 0 to 20.3average lowest 
compartment, 16.7°; highest, 18.2° C. After 37 days' incubation only 
one tuber showed a rot; this was at an average temperature of 18.2° C. 
The organism was recovered. / 
The thirty-eighth day after inoculation the remaining tubers were 
exposed to an average temperature of 22.8° C. for the succeeding 19 days. 
At this time all inoculated tubers were rotted, all stages of wet-rot and 
dry-rot being represented. The Netted Gems were more badly affected 
than the Burbanks. In every case the organism was recovered where 
the attempt was made, four reisolations being identified. 
F. radicicola 2890; isolated in October, 1913, from a jelly-end rotted 
tuber of the Burbank variety from Watsonville, Cal. (associated with 
Rhizoctonia sp. 2892). Culture used, 9-day-old pionnotes on a stem of 
Melilotus alba . All inoculated tubers showed a progressive rot begin¬ 
ning at the inoculation prick (PI. XVII) after 20 days' incubation at an 
average temperature of 23 0 C. The lenticels were invaded and the 
sprouts infected and dropping off. Some of the tubers were completely 
softened, only a slimy mass remaining in the entire skin. The organism 
was recovered by six reisolations. 
