GREENHOUSE AND COLD FRAME FUMIGATION 137 



numerous insecticides, hydrocyanic acid gas was used. 

 The work was placed in the hands of H. D. Hemen- 

 way. All the results obtained were not conclusive, 

 and it is impossible to give definite details relative to 

 future work. Some of these results, however, are in- 

 teresting, and are given herewith. Other tests should 

 be made. 



After several preliminary experiments with some 

 of the more delicate plants in a wooden box, two 

 rooms, known as the stove and cactus, were fumigated 

 at the same time, the connecting doors between them 

 having been opened. Many of the cacti were infested 

 with the common cactus scale, Diaspis cacti. In the 

 stove-room, all through the twining vines, were white 

 waxy threads protecting the eggs and young mealy 

 bugs. 



The cactus-room contained 7,076 cubic feet of air 

 space and the stove-room 7,357 cubic feet. Forty 

 ounces of potassium cyanide were used in each room, 

 and they were kept closed for thirty minutes. The 

 ventilators, which had been previously prepared, were 

 then opened from the outside. The temperature of 

 the house was about 60 F. The conditions of the 

 weather were perfect for such a test, as it was rain- 

 ing, the water filling all the cracks in the house, and 

 thus preventing the escape of the gas. It was also 

 warm outside, so the house was not cooled too low 

 while the ventilators were open. It was perfectly 

 dark. The ventilators were left open for about an 

 hour, and closed for the night. 



The room contained many different kinds of cacti, 

 begonias in variety, passifloras, allamandas, bananas 



