Dec. 10, 1913 
Foot-Rot of the Sweet Potato 
259 
None of the checks became diseased. The experiment was terminated February 
28, 1913. 
Experiment No. 14. —On May 9 seven sweet-potato plants in pots in the green¬ 
house were inoculated by inserting the hyphae (no pycnidia in the culture ) of organism 
No. 101 (culture No. 2 of May 5) into the lower part of the stem. Six plants were left 
as checks. 
Results.—On May 31 six plants, and on June 4 one, or a total of seven plants, were 
infected. None of the checks were diseased. When the experiment was terminated 
on June 5, pycnidia were abundant on the stems of all diseased plants. 
Experiment No. 15.—On September 3 six sweet-potato plants in pots in the 
greenhouse were inoculated by inserting spores and hyphse of organism No. 101 (cul¬ 
ture No. 13 of Aug. 14) into the vine at the node 3 to 4 feet from the hill. Five other 
vines were wounded with a sterile needle and left as checks. 
Results.—On September 25 five of the vines were infected at the point of inoculation. 
The organism had spread 2 inches or more each way from the point of inoculation. 
None of the checks were diseased. The experiment was terminated October 5, 1913. 
Experiment No. 16.—On September 3 five sweet-potato plants in pots in the green¬ 
house were inoculated by inserting spores and hyphae of organism No. 108 (culture 
No. 17 of Aug. 18) into a vine at the node 3 to 4 feet from the hill. The checks were 
the same as those used in experiment No. 15. 
Results.—On September 25 all the vines were infected at the point of inoculation, 
the organism spreading as in experiment No. 15. The experiment was terminated 
October 5, 1913. 
INOCULATIONS PROM REISOLATIONS 
Experiment No. 17.—On October 5 twelve young sweet-potato plants in pots were 
inoculated by inserting pycnospores and hyphae of organism No. 102 1 (culture No. 2 
of Sept. 25) into the lower part of the stem. Ten plants pricked with a sterile needle 
were left as checks. 
Results.—On November 5 five plants, on November 11 one, on November 13 one, 
on November 15 one, on November 25 one, and on December 9 three, or a total 
of all 12 plants, were infected. None of the checks were infected. Pycnidia were 
found on ten of these plants when lifted and developed on the other two after three 
days in a moist chamber. The organism was recovered in pure cultures from seven 
plants. The experiment was terminated on December 9, 1913. 
Experiment No. 18.—On January 23 eight young sweet-potato plants in pots were 
inoculated by inserting pycnospores and hyphae of organism No. 108 2 (culture No. 2 
of Jan. 11) into the lower part of the stem. Six plants were left as checks. 
Results.—On February 28 one plant, on March 8 two, on March 13 four, and on 
March 28 one, or a total of eight plants, were infected. Pycnidia were present on seven 
of the diseased plants when lifted and developed on the other one after 10 days in a 
moist chamber. None of the checks were diseased. Experiment terminated March 
29, 1913. 
Experiment No. 19.—On February 19 ten young sweet-potato plants in pots were 
inoculated by inserting pycnospores and hyphae of organism No. 108 (culture No. 3 of 
Jan. n) into the stem. Seven plants were left as checks. 
Results.—On March 21 four plants, on March 24 one, on March 31 one, on April 4 
one, on April 18 one, and on April 26 one, or a total of nine plants, were infected. 
1 The organism recovered from plants inoculated in the greenhouse on Aug. 26 with No. 100 is known 
as No. 102. 
2 When the plants, inoculated on the Potomac Flats on Aug. 26, 1912, were dug, they were placed 
with the roots attached in moist chambers in the laboratory. After several weeks the fungus grew from 
the stem into the roots (PI. XXIII, B), from which it was recovered. This organism was numbered “108." 
17072 —13-6 
