GREENHOUSE AND COLD FRAME FUMIGATION 127 



large house (15,587 cubic feet), one-tenth (o. 10) 

 gramme cyanide was used. In case of the double 

 English violets, infested with plant-lice, slugs, milli- 

 pedes, leaf-eating larvae, cutworms, red spiders, etc., 

 fifteen hundredths (0.15) gramme was used, and ex- 

 posed twenty minutes. All the insects were destroyed, 

 excepting a few red spiders, and even these were kept 

 down by frequent fumigation. 



EffeEls on foliage. The foliage of single violets, 

 like California, Princess of Wales, and the like, is some- 

 times slightly injured with the stronger dose of 0.15; 

 a weaker amount, one-tenth (o. 10) gramme should be 

 used for these single varieties. Roses, especially the 

 younger growths, are very sensitive, and slight injury 

 has been noticed even where the smallest dose (0.075 

 gramme) was used. Carnations will stand one- tenth 

 (o. 10) gramme for fifteen minutes; but more careful 

 experiments are needed before the gas is generally 

 recommended for either carnations or chrysanthe- 

 mums. 



Grapes, under glass, in New Zealand, have been 

 fumigated at the rate of nine-hundredths (0.09) 

 gramme over night, infested with mealy bugs, with 

 good results. It has also been used successfully by 

 Dr. J. Fisher on tomatoes infested with the white fly. 

 He used one ounce cyanide (28.35 grammes) for 

 1,000 cubic feet, and left the plants exposed over 

 night without injury. The writer fumigated a green- 

 house in Maryland in which cucumbers were growing 

 and badly infested with the melon louse (Aphis 

 gossypii). The house was filled with gas at sundown, 

 using fifteen-hundredths (0.15) gramme of cyanide per 



