71 



insects were mostly killed, but some of the plants were badly injured. 

 This was especially true in case of the smilax, the upper leaves of the 

 carnations, and the lettuce. Much of the latter, which was very small 

 and in full light, was killed, while some that was shaded showed much 

 less injury. The smilax and carnations recovered in time, but received 

 a severe check. As will be seen later, smilax and more delicate plants 

 have been subjected to double the strength of gas in darkness without 

 injury. 



EXPERIMENT I. 



Conditions. — Made Nov. 27, 1897, in sunlight, in a glass box contain- 

 ing nearly 42 cu. ft. The following proportions were used: 2.1 grams 

 (L oz. cyanide of potassium to 570 ft.) of potassium cyanide, liberated 

 with 2.1 cc water and 2.1 oc sulphuric acid; temperature of box, 63° F.; 

 plants treated were Asparagus plumosus, veronicas, roses, cinerarias, 

 begonias, and chrysanthemums; the insects upon these plants were 

 mealy bug, " green fly," scale, and Fuller's rose beetle {Aramigus fulleri) ; 

 there were 2 plants each of smilax and roses, one sprinkled with 

 water, the other dry. The box was closed for 30 minutes. 



Results. — Some of the green flies commenced to drop in three minutes. 

 There was no apparent injury at close of fumigation, but December 2 

 nearly all plants showed some injury. Most of the insects were killed, 

 but the rose beetles were not much injured. 



EXPERIMENT II. 



Conditions. — Made November 27, 1897, in same glass box; in dark- 

 ness; potassium cyanide used, 1 oz. to 285 cu. ft., with same proportions 

 of acid and water as before; temperature 55° F. ; time fumigated, 

 25 minutes ; plants used : 2 genistas, 2 cupheas, 2 veronicas, and 2 

 coleus; insects: mealy bug, green fly, white-tailed mealy bug, scales 

 {Aspidiottis rapax and A. Jicus). 



Results. — All insects dead; no injury to any of the plants. A com- 

 parison of these two experiments shows that the first lot treated in 

 sunlight were all injured while those treated in darkness with double 

 the strength of hydrocyanic acid gas were uninjured. 



EXPERIMENT III. 



Conditions. — Made November 28; glass box; dark; potassium cyan- 

 ide used, 1 oz. to 190 cu. ft., with 1 oz. water and If oz. sulphuric acid 

 (see table); temperature, 47° F. ; time fumigated, 20 minutes; plants: 

 calla, ferns, cineraria, genista, cuphea, camphor tree; insects: scale, 

 rose beetles, mealy bug, and aphis. 



Results.— All insects excepting rose beetles killed; no plants injured. 



EXPERIMENT IV. 



Conditions. — Made November 29, 1897 ; glass box; darkness; potas- 

 sium cyanide and conditions same as in No. Ill (see table); time 

 fumigated, U0 minutes. In this experiment an attempt was made to 

 watch the effects on Fuller's rose beetle. 



