202 REPORT OF THE BOTANICAL DEPARTMENT OF THE 
Third spraying.—The third spraying was made July 29. By 
this time the vines were so large that the branches of plants in 
adjacent rows touched. Potato beetles were well under control 
and there were no flea-beetles. Series II and III were again 
treated as in the first spraying, except that a larger quantity of 
Spray mixture was used. On Series IV and V the treatment 
was the same as in the first spraying except that the bordeaux 
was made by the 6—4—50' formula.?® This time all spray mixtures 
were applied at the rate of 175 gallons per acre. On July 31 the 
‘rainfall was .02 inch and on August 1, .52 inch. 
Fourth spraying.—This spraying was made August 12. The 
day being bright, the spray dried on the foliage quickly. The 
rows of Series I, II and [III were much affected with late blight. 
On Series III less lime was used in this spraying than in former 
ones, the formula this time being one pound paris green, one 
pound lime, fifty gallons water. The other three series were 
treated as in the first spraying. All applications in this spraying 
were at the rate of 225 gallons per acre. Following this spray- 
ing rain fell on August 13, 16, 17, 19 and 20. 
Fifth spraying—tThe fifth and last spraying was made August 
25. There were no flea-beetles and no Colorado potato beetles. 
The rows of Series If and III were now so much affected by 
blight that it would be difficult to detect paris green injury 
should any occur. Consequently, there was no object in using 
paris green, and so it was omitted in this spraying. In spite of 
the frequent rains since the fourth spraying the rows of Series 
IV and V were still so thoroughly covered with bordeaux that 
they scarcely needed spraying. However, it was done with the 
bordeaux prepared as in the first spraying, the rate of applica- 
tion being 200 gallons per acre. 
Chemical analysis of the paris green.—Paris green is variable 
in chemical composition. The greater the percentage of soluble 
arsenic contained in it the greater the liability of its injuring 
foliage.* Hence it is important to know the chemical composi- 
Six pounds of copper sulphate, four pounds of lime and 50 gallons of 
water. 
J. K. Haywood has reported (U. S. Dept. Agr. Bureau of Chemistry Bul. 
82) the results of some paris green spraying experiments which “ were 
undertaken to show how much soluble arsenious oxide may be present in 
samples of paris green used for spraying purposes without injury to the 
foliage” of certain fruits. So far as known to the writers no such work 
has been done for the potato plant. 
