8 4 
Journal of Agricultural Research 
Vol. V t No. a 
the latter place. A plot of ground was selected that had been lying 
idle in 1913, but which before had grown several crops of potatoes in 
succession. 
Tubers of the Green Mountain variety showing all stages of infection 
by P. infestans were selected on May 25 from potatoes grown and held in 
storage throughout the winter in potato cellars at Caribou. Most of 
them were badly infected, as was natural to expect at this late date. 
Many had only one living eye, while others, of course, had several. 
Both whole and cut seed were planted in the same way as already de¬ 
scribed in the field tests of 1913. In one row 170 whole tubers were 
planted and 363 in two rows adjoining. On each side of these three 
rows two rows were planted with sound seed as checks, also of the Green 
Mountain variety. The planting was made on June 2, when the soil 
was drier than usual. There was very little rain until July 20, when an 
inch fell, but, as a whole, the season was drier than that of 1913 and 
therefore was less favorable for the development of late-blight. 
An examination made on July 15 showed that 47.6 per cent of the 
whole infected tubers, 37.4 per cent of the cut infected seed, and 92 per 
cent of the healthy seed in the four adjoining rows came up. The low 
percentage of germination of the infected seed was probably due to two 
factors, the large amount of infection of the seed with P. infestans and 
the dry weather following planting. The infected seed rotted in the 
ground in the same way as described in the studies made in 1913. 
The first case of infection by this fungus was discovered on July 22, 
two days after a heavy rain had fallen. It was in a hill grown from a 
whole infected tuber having nine shoots from 12 to 18 inches tall. Five 
of the smaller shoots were found to be infected at and below the surface 
of the soil. The soil was carefully removed from about the hill, and two 
of the five were found to be discolored all the way from the mother 
tuber up to the surface of the soil. The three others seemed to have 
become infected at the surface of the soil, probably by spores borne on 
the two shoots most generally infected. The infection of neighboring 
stems in the same hill above the surface of the soil was also noted in the 
field studies of 1913. 
Two days later another hill, also grown from whole seed, was found to 
be infected. This had 14 shoots, varying from 10 to 18 inches high. 
The smallest shoot was discolored in the same way as described in the 
previous case, and upon further investigation the infection was found 
to extend down to the parent tuber. The fungous infection was evident 
by the glistening white growth on the stem just above the surface of the 
soil. None of the older shoots in this hill were infected at this date. 
On July 26 one of four shoots in a hill grown from cut seed was found 
to be infected. These four shoots ranged from 6 to 14 inches in height. 
Two of the smallest shoots in this hill were infected with P. infestans. The 
