248 
Journal of Agricultural Research 
Vol, VII, No. 5 
of sterilized sweet-clover stems. The results obtained confirmed the 
examinations made direct from the plates. The 38 colonies on both the 
agar and the sterilized sweet clover in all the test tubes proved to be a 
species of Phoma. Inoculations were also made with one or more of the 
fungi from each group, which showed that only the fungus included in 
the 38 colonies was pathogenic. 
Table XIV .—Results of isolations f rom tubers showing typical lesions caused by the rot 
of Phoma sp. 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
T 3 
14 
r 5 
16 
17 
18 
T 9 
20 
Plate No. 
Number 
of colo¬ 
nies 
Number of growths 
produced on plate. 
growing 
on plate. 
Bacterial. 
Fungus. 
A 
0 
A 
O 
0 
O 
0 
0 
O 
0 
0 
O 
0 
O 
O 
A 
0 
A 
2 
0 
2 
7 
O 
O 
I 
0 
O 
I 
A 
2 
2 
2 
0 
2 
2 
0 
2 
• 
4 
4 
O 
4 
O 
4 
A 
O 
A 
4 
O 
A 
7 
O 
3 
0 
• 
2 
7 
A 
0 
0 
A 
4 
I 
2 
O 
Total 
53 
6 
46 
INOCULATION OF TUBERS WITH PHOMA SP. 
As the fungus was obtained from the tuber, a series of inoculations was 
made on tubers, which were selected, washed, and immersed in mercuric 
chlorid (1:1,000) for 10 minutes, or in some cases in 85 per cent alcohol and 
burned over the surface. By means of a flamed scalpel the tuber was cut to 
a depth of 1 to 3 cm., a piece of a pure culture from a transfer 4 days old 
inserted, and the point of inoculation marked with india ink, after which 
the potatoes were placed in a moist chamber at ordinary room temper¬ 
atures. At the end of four days the first indications of the disease became 
apparent. Ten days after inoculation the lesions reached 6 mm. in diam¬ 
eter. The diseased spots developed until they were from 12 to 25 mm. in 
diameter, but after this made little or no progress. The control tubers, 
treated in a similar manner but with no fungus inserted in the wound, 
remained healthy throughout the entire experiment. The writers have 
