A Dry Rot of the Irish Potato Tuber 65 
new tubers were examined at frequent intervals but no sign of 
dry rot appeared. After the tops died, forty of the tubers, with 
the soil still clinging to them, were placed in moist chambers 
but no dry rot appeared on any of them. 
ARTIFICIAL INFECTION. 
During the summer of 1909 at Alliance inoculations with 
Fusarium tuberivorum were made, in the held, into the growing 
plant and the newly forming tuber. The tirst inoculations were 
made July -9 when the plants were in prime condition. New 
tubers, three to five centimeters in diameter, were carefully 
separated out by themselves, wiped clean with cotton, inocu- 
lated, and then paper placed around them to prevent contamina- 
tion. One tuber on each of ten plants was inoculated once. 
Four inoculations were also made into the stalks of these same 
plants below the soil level. The soil was carefully replaced over 
the tubers and around the plant in a manner comparable to the 
surrounding conditions. The plants were not injured in this 
way and growth was not retarded. Examinations were fre- 
quently made but no infection was found to take place. 
In January, 191U, inoculation experiments were carried on 
under greenhouse conditions. Paraffined baskets were used 
which were large enough to hold about fifteen kilograms of soil. 
All paraffined baskets were washed with mercuric chloride and 
filled with sand which had been autoclaved for one-half hour at 
115° C. Potato tubers which were treated with mercuric chloride 
were simply wiped off with cotton or allowed to dry after a 
wetting in the solution. The knife used in cutting was heated 
and cooled between the cutting of the different tubers. In two 
baskets the seed pieces were taken from healthy tubers and a 
pure culture of b murium tuberivorum placed upon the cut sur- 
face of each piece. Sixteen days after planting, the plants were 
examined. One seed piece was "crumbly" and rotted and the 
plant was small and worthless. Anoter seed piece was slightly 
infected but the plant produced was in fair condition of growth. 
Three other seed pieces were not at all infected and produced 
strong healthy plants. Twenty-three days after planting neither 
the new tubers nor the plants showed any infection but all the 
old seed pieces showed a slight rotting. After the plants had 
grown for two months in two other baskets they were inoculated 
just below soil level with Fusarium tuberivorum. No infection 
resulted. 
During the winter of 1911-1912 inoculations of very young 
shoots were made in the laboratory. None of these were success- 
ful. These were made because an apparent infection had taken 
3 
