12 INJURY TO VEGETATION BY SMELTEE FUMES. 



and carbon disulphid used in burning give off enough heat to raise 

 the temperature of the chamber above that of an ordinary green- 

 house. After an hour of this treatment the door was opened and the 

 air in the box pumped out by means of the fan. The process was 

 then repeated, so that each plant received from three to four fumiga- 

 tions per day. At night the plants were removed from the fumi- 

 gation chamber. Control plants were always placed alongside the 

 fumigation chamber, and these were removed from the room during 

 the time that the sulphur dioxid was being pumped out of the cham- 

 ber. Potted Australian pines of about three years' growth and young 

 cowpeas were used in the experiment. The following results were 

 obtained : 



(a) Pine tree. Fumigated with 1 part of sulphur dioxid to 100 parts 

 of air (by weight). After 3 one-hour fumigations the needles began 

 to droop badly and turned from a bright to a gray, green. After 6 one- 

 hour fumigations practically all of the needles were drooping and 

 nearly all had turned either yellow or brown. The pine was evi- 

 dently badly injured, although the control plant was in good condition. 



(6) Pine tree. Fumigated with 1 part of sulphur dioxid to 1,000 

 parts of air. After 3 one-hour fumigations the pine needles began to 

 droop and some to turn yellow. After 9 one-hour fumigations all of 

 the needles were drooping and had turned brown and j^ellow. Tree 

 evidently badly injured, although control plant was in good condition. 



(e.) Pine tree. Fumigated with 1 part of sulphur dioxid to 10,000 

 parts of air. After 25 one-hour fumigations the pine needles began 

 to droop, and some were slightly grayish and others brownish. After 

 50 one-hour fumigations a large number of the needles had turned 

 brown, and the remainder looked extremely unhealthy. This same 

 pine was now fumigated with 1 part of sulphur dioxid to 30,000 parts 

 of air. After 18 such fumigations it was removed and found to have 

 been greatly injured. About one-half of the needles were brown and 

 dead and the remainder were sickly looking and yellow. The con- 

 trol plant was in good condition. 



(d) Two cowpeas. Fumigated with 1 part of sulphur dioxid to 

 10,000 parts of air. After 3 one-hour fumigations about one-half the 

 leaves of both had shriveled up and fallen. After 18 one-hour fumi- 

 gations all of the leaves of both plants had shriveled up and fallen. 

 The cowpeas were then subjected to three or four more fumigations 

 of the same strength and taken out and watered to see if they would 

 grow again, but they could not be revived. The control cowpeas in 

 this experiment were in good condition. 



(e) Pine tree. Fumigated with 1 part of sulphur dioxid to 30,000 

 parts of air. After 50 one-hour fumigations the needles were droop- 

 ing, and most of them looked yellow and sickly. 



This experiment was not continued further, it having been shown 

 to the author's satisfaction that extremely minute quantities of sul- 

 phur dioxid were injurious to vegetation. 



