c 
10 FUMIGATION METHODS 
the fall, midwinter, and early spring, and now we took 
up the effect of the gas on the trees in late spring as 
the buds began to open. 
Work upon nursery stock.—Experiments were also 
performed the spring of 1899 upon nursery stock, for 
the purpose of determining the precise effect of the 
gas upon young trees used at a strength greater than 
0.25 gramme cyanide per cubic foot. Owing to the 
fact that some states stipulate by law that trees must 
be fumigated, it became absolutely necessary that we 
know definitely the effect of this gas upon growing 
plants, especially dormant trees. No recent experi- 
ments have been recorded along this line, as far as I 
know. We have been using 0.25 gramme cyanide in 
general work, and I recommend that strength for all 
nursery stock above three feet in hight. 
Apple trees.—We began our experiments with the 
stronger doses March 29, 1899. ‘The apple trees were 
divided into twenty different lots of five trees each, 
leaving five for a check. ‘They were 4 to 5 feet 
in hight, and of the following varieties: Ben Davis, 
Northern Spy, Limbertwig, Wealthy, Fall Pippin, 
Oldenburg, Stark, Rome Beauty, Schockley, and York 
Imperial. They were exposed in gas one hour, and 
each lot was fumigated with 0.25, 0.30, 0.40, 0.45, 
and so on, adding 0.05 to each one until we reached 
1.00, then skipped from 1.00 to 1.25, 1.35, and 1.45 
grammes, thus completing the series. The trees were 
labeled and planted, and were under observations two 
seasons. 
The outcome of these experiments is as fol- 
