330 
Journal of Agricultural Research 
Vol. XI, No. 7 
yield of fruit than the normal. At the close of the experiment the total 
weight of ripe fruit was less for the normal than for either of the fumigated 
sets. 
It was thought desirable to obtain similar data on a quick-growing 
plant like lettuce. Small plants were set into boxes similar to the ones 
used in the above experiment with tomatoes, and divided into three 
sets. No. 19 was a 
normal set. No. 20 
was fumigated with 
0.25 gm. of potassium 
cyanid per cubic me¬ 
ter overnight, without 
apparent injury. No. 
21 was fumigated with 
the same dose for one 
hour in bright sunlight. 
This set was severely 
injured, almost all of 
the mature leaves 
being burned. Samples 
for the determination 
of dry weight were 
taken every three to 
five days until the 
plants were f ully grown. 
The data obtained are 
expressed graphically 
in figure 9. There ap¬ 
pears to be practically 
no difference between 
the normal and the set 
fumigated without in¬ 
jury. The set which 
was severely injured 
was noticeably retard¬ 
ed, but soon recovered 
its power of growth and 
reached maturity about one week after the two other sets. 
From these results it appears that the growth factor in tomatoes 
at least is stimulated by hydrocyanic-acid fumigation. This is mani¬ 
fested not only in total dry weight of plants but in ripe fruit produced 
as well. These experiments further show that in greenhouse practice 
severe injury to plants may be not so serious as might appear, since the 
plants, after a temporary setback, grow with increasing vigor to maturity. 
/■& 
/j 
Fig. 8.—Curves showing the production of fruit by the three sets of 
tomato plants in figure 7. 
