1 6 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, L,imbertwig, 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 

 i. oo, then skipped from i.oo 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- 



