66 
work was done injured. In fact, from the results of fumigating plants 
before setting them out, we believe that strawberry plants in the field 
would stand a strength of two-tenths or three-tenths of a gram KCn 
per cubic foot for twenty or twenty-five minutes, were that necessary. 
Work done with a wooden box 2 by 2 by 24 feet, with open bottom, 
in fumigating loose strawberry plants infested with Apis forbes’. 
brought out the influence of the soil on the gas and the ready diffa- 
sion in a cubical space. In this box two-tenths gram KCn per cubic 
foot in ten minutes, three-tenths gram in five minutes, and one-tenth — 
gram in twenty minutes proved fatal to the aphides. 
Thus, in the 10-foot frame, with a soil surface of 20 square feet and 
a cubic capacity of 84 feet, or a ratio of 23 soil surface to 1 of vol- 
ume, Just twice as much gas was required to be generated from two 
points to be effective as that in the wooden box of 10. cubic feet 
capacity and 5 square feet soil surface, having an almost opposite 
ratio of 2 volume to 1 of soil surface. Again, the covers for indi- 
vidual plants, with a soil surface of about 3 square feet and a capacity 
of one-half cubic foot, or a ratio of 6 soil surface to 1 of capacity, 
required eight-tenths gram per cubic foot, or four times as much. 
Comparing these figures with the results obtained in the laboratory 
test of the influence of the soil, by a rough calculation a rule some- 
what as follows might be deduced: Let « equal the mean height 
in feet: then the amount of cyanide of potassium per cubic foot 
expressed in decigrams would be 2 plus the reciprocal of «x, or the 
. < e uw rc if 
decigrams of KCn to be used per cubic foot equals ae 
Whether these ratios would hold true for a larger series of tests 
remains to be ascertained, but they at least indicate the general tend- 
ency of the diffusion of the gas and the influence of the soil upon it. 
The cost of such frame is but little. The materials for them should 
not cost over 25 or 30 cents, and they are easily made. With rows 3 
feet apart, using 12 frames, with three-tenths gram per cubic foot for 
ten minutes, an acre could be covered in about two days at a cost of 
about $3 for chemicals. This treatment is practicable, therefore, only 
upon plants of some considerable value and for relatively small areas. 
Under many circumstances, however, it could be used to much better 
advantage than any other means of combating a pest, and often might 
be found effectual where no other method of extermination were 
possible. 
NOTES FROM DELAWARE. 
By E. Dwieur Sanperson, Newark, Del. 
The harlequin cabbage bug.—TYhe harlequin cabbage bug has been 
under observation as much as the scarcity of material would permit. 
Last year the bugs were not noticed till late in the summer, and injury 
by them, as noted in one or two instances, was confined to very late 
