Nov. 12, 1917 
Greenhouse Fumigation with Hydrocyanic Acid 
329 
To obtain more definite data on this point, a longer experiment with 
tomatoes was conducted, carrying them through their complete life cycle. 
Three sets (No. 16, 17, and 18) were selected according to uniformity in 
size and vigor. Wooden boxes 16 inches square and 12 inches deep were 
filled with rich soil and six plants in each allowed to attain a height of 
about 6 inches before the experiment was started. There were 10 boxes 
in each set. Set 16 was kept as a control. No. 17 was fumigated with 1.5 
gm. of potassium cyanid per cubic meter for one hour during the night, 
with curtains drawn 
tightly. The effect of 
the fumigation was a ^ 
severe curling of the 
leaves and a burning of 
the youngest leaves (PI. ^ 
34, A). No. 18 was | 
fumigated threetimesat ** 
two-week intervals with 5 
0.25 gm. of potassium ^ 
cyanid per cubic meter 0 
overnight. No injury 
resulted from any of ^ 
these. Each week from ^ 
three to six plants from ^ 
each set were taken, and | 
their dry weight was de- ^ /<s 
termined. The growth ^ 
curves in figure 7 give § 
these data. The plants 
were controlled to one 
growing stem,and at the 
end of seven weeks had 
reached the top of the 
greenhouse. The plants 
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7. — Growth curves of three sets of tomato plants as affected 
by hydrocyanic-acid fumigation. 
As it was decided to follow the subsequent history of the sets by 
the quantity of ripe fruit produced, the growing point was cut off 
and all adventitious buds kept removed. Later, when the green fruit 
had begun to set, a number of large leaves from each plant were re¬ 
moved to admit more light. The daily production of ripe fruit is shown 
in figure 8. Attention should be called to the fact that set 18, fumigated 
without injury, produced fruit two weeks earlier than the normal, and 
that almost throughout the experiment both fumigated sets had a higher 
