9 ° 
Journal of Agricultural Research 
Vol. V, No. a 
ing of August 17, 1911, after a spell of wet weather, two potato plants were 
sprayed with a suspension of spores of P. infestans , the spores having been 
taken from infected plants in the greenhouse. The inoculation of the 
two plants was made in the usual way and typical spots became visible 
in the course of five days. The amount of infection was not extensive. 
The ground was very moist, owing to the fact that several rains had 
fallen the previous week, and the weather was continuously cloudy from 
August 22, the date in¬ 
fection first appeared, 
until August 27. 
On August 30 infec¬ 
tions were found on 
two plants adjoining 
those artificially in¬ 
fected, and the next 
day four more plants 
immediately adjoin¬ 
ing showed infection 
on several leaves. 
Careful examination 
showed no infection on 
any of the plants far¬ 
ther away. The new 
infections that had oc¬ 
curred on August 31 
were on the six plants 
immediately sur¬ 
rounding the two arti¬ 
ficially infected. The 
fungus had made no 
further spread in the 
Fig. 3— A portion of the same section of a potato plant shown in half-acre DO tat O plot, 
figure i, showing the mycelium in the pith region of the stem. * r 
After August 30 new 
infections were daily found farther and farther from the two plants first 
infected, and on September 7 infected leaves could be found everywhere 
throughout the plot, though none of the vines were conspicuously 
blighted. By this time all the plants within a radius of 8 feet of the two 
plants initially infected were killed. Farther away the infection was 
much less in extent, though present in abundance. By September 12 the 
plot was very badly blighted; not a single plant anywhere was free from 
infection, and many were wholly dead. No further records except as to 
the time of harvesting and the amount of loss were kept when the tubers 
were harvested on October 10. Less than 50 per cent of the crop was fit 
to put in storage, and less than 10 per cent kept until spring, although 
held in good storage. 
