274 
Journal of Agricultural Research 
Vol XXVI, No 6 
Table I .—Nature and results 
of experiments conducted to prove the pathogenicity of the 
fungus from udo 
Date inoculations 
were made. 
Number 
of plants 
inocu¬ 
lated. 
Number 
of con¬ 
trols. 
Where 
growing. 
Method of inoculation. 
Number 
of in¬ 
oculated 
plants 
infected. 
Number 
of con¬ 
trols in¬ 
fected. 
Mar. 30, 1921... 
5 
5 
Green- 
Inserted hyphae in 
3 
O 
house. 
wounds. 
May 13, 1921. . . 
15 
10 
...do... 
.do. 
Do. .. 
10 
10 
...do... 
Placed hyphae against 
None. 
O 
root; no wound. 
Apr. n, 1922... 
10 
10 
...do... 
Inserted hyphae in 
10 
0 
wounds. 
May 17, 1922.... 
20 
10 
...do... 
.....do. 
2 
O 
Do. /. 
5 
10 
...do... 
Placed hyphae against 
None. 
O 
root; no wounds. 
May 24, 1922.... 
3 
3 
Field.. 
Inserted hyphae in 
1 
O 
wounds. 
An examination of Table I shows that only in the experiment begun 
on April ii, 1922, was 100 per cent infection obtained. In another case, 
begun May 17, 1922, only 2 plants out of 20 became infected. The 
small percentage of infection in this case is attributed to too high tem¬ 
perature, since a correlation was always apparent between the temper¬ 
ature and the number of plants infected. In no case was infection 
obtained in unwounded plants. Wounds through which the fungus can 
enter seem to be necessary. Too small a number of tests were made, 
however, to establish this point conclusively. The largest number of 
plants became infected when they were growing vigorously and the 
temperature was fairly low, as was the case in the experiment con¬ 
ducted in April, 1922. Infection became evident in the inoculated 
plants in from three days to two weeks. The softening of the root and 
the discoloration of the stem were the first symptoms. These were fol¬ 
lowed by wilting, yellowing, and finally a browning of the leaves, as 
previously described. In one experiment the fungus had in 6 days 
penetrated the tissues of the host for a distance of 2 to 3 inches above 
and below the point of inoculation. The plants used in this case were 
about a year old; they were growing in pots and had been placed out 
of doors during the winter months. In the early spring they were 
brought into the greenhouse, where they began to make a vigorous 
growth almost at once; so that at the time of inoculation they were 
about 2 feet high. The writer had little success in growing these plants 
unless each winter they had been subjected for a time to a freezing 
temperature. 
The infected stems lost their dark green color, becoming grayish 
and water soaked, gradually changing to yellow, and finally to brown. 
The external tissues of the infected stem usually remained firm to the 
touch, owing to the presence of the large quantity of vascular tissue 
located just beneath the epidermis, but the stem has a large pith, which 
was soon softened. The cells of the pith were plasmolyzed and fell apart, 
showing that the middle lamellae of the cells had been dissolved. The 
decayed tissue was filled with large, densely granular hyphae, which 
appeared to find here a very favorable medium for growth. The break¬ 
ing down of the middle lamellae and consequent softening of the tissue 
