118 REPORT OF THE BOTANICAL DEPARTMENT OF THE 
hilly, Mr. Pettit thought best to fit the sprayer for use with two 
horses. The dates of spraying in the field in which the test 
rows were located were as follows:—July 20, August 1, 18 and 
25 and September 7. The bordeaux used was made by the usual 
formula; namely, six pounds of copper sulphate, four pounds of 
lime and fifty gallons of water. The eight-acre field was about 
100 rods from the water supply, but the smaller field was 
nearer. There were so few bugs that it was unnecessary to use 
poison. 
Mr. Pettit states that the unsprayed rows began to show blight 
about August 18. When one of the writers examined the ex- 
periment on August 24 the unsprayed rows showed no marked 
contrast to the sprayed, but upon going among the plants it was 
readily seen that blight was thoroughly established throughout 
the greater part of the length of the rows. At the south end 
one-third of the foliage was ruined by blight. The sprayed 
plants, also, showed a little blight, but they were not nearly as 
bad as the unsprayed. 
On September 21, the day before frost, the condition of the 
plants was as follows:—Throughout one-fifth of the distance 
across the field from the south end the unsprayed rows were com- 
pletedly dead and dry. In the same region the plants on the 
sprayed rows adjacent still retained about one-third of their fol- 
lage. Over the next two-fifths of their length the unsprayed rows 
were dead, but the stems of the plants were still succulent. 
Spraved plants adjacent were about half dead. Over the remain- 
ing two-fifths of their length the unsprayed rows were half dead 
while the sprayed rows adjacent were uninjured by blight. (Plate 
IX, fig. 1, shows the test rows at the south end as they appeared 
on September 6.) 
All of the damage was caused by late blight, Phytophthora 
infestans. The greater virulence in the southern portion of the 
field seems to have been chiefly due to the influence of a piece 
of timber on’ the south. Plants next the timber were shaded for 
two hours or more every morning. Consequently, both dew 
and rain remained longer on these plants, thereby furnishing 
excellent conditions for the growth and propagation of the blight 
fungus. Plants next the timber blighted first and then the dis- 
ease spread toward the north. 
