SULPHUR-TRIOXID CONTENT OF FOLIAGE. 13 



No. 5292. White oak. — Fumigated IG times from July 20 to oU.y 24 with sul- 

 phur dioxid 1 : 10,000. After 2 fumigations brown spots appeared on the leaves. 

 After 5 fumigations the top leaves were dry and brown. After IG fumigations 

 all the leaves were dry and brown. The control plant was uninjured. 



No. o29Jf. ScruJ) pine. — Fumigated twice on July 25 with sulphur dioxid 

 1 : 10,000. After 2 fumigations all the leaves were brown, dry, and dead. The 

 control plant was uninjured. 



No. 5296. Black oak. — Fumigated 100 times from August 5 to August 30 with 

 sulphur dioxid, 1 : 50,000. After 20 fumigations the gloss disappeared from the 

 leaves and the young leaves took on a grayish tint. After 100 fumigations all 

 the end buds were killed. The younger leaves were bleached and dotted with 

 brown spots. The old leaves had lost their gloss and were bleached in spots. 

 This tree was observed for three weeks after its removal from the fumigation 

 chamber and no new growth took place. The control plant was uninjured. 



No. 5298. Scrub pine. — Fumigated 34 times from September 3 to September 

 10 with sulphur dioxid 1 : 50,000. After 9 fumigations the top needles were 

 somewhat bleached. After 19 fumigations the top needles were entirely killed 

 and the lower needles were killed at the ends. After 34 fumigations all leaves 

 were brown and dry. The control plant was uninjured. 



No. 5300. Scruh pine. — Fumigated 96 times from September 12 to October 7 

 with sulphur dioxid 1 : 100,000. After 49 fumigations the ends of the young 

 needles were turning brown. After 96 fumigations all the leaves were badly 

 affected, the young needles were brown and dead, the older needles dead at the 

 ends. The control plant was uninjured. 



The investigation of the effect of fumigation on plants growing in 

 the open was discontinued at this point on account of a pressure of 

 other work, but will probably be resumed later and even greater 

 dilutions than 1 : 100,000 will be used. 



SULPHUR-TRIOXID CONTENT OF THE FOLIAGE OF FUMIGATED 

 AND UNFUMIGATED PLANTS. 



It was next necessary to determine whether treating plants with 

 sulphur dioxid increased the sulphur-trioxid content of the leaves so 

 that it was present in larger quantities in the leaves of the treated 

 plants than in those of the untreated ones. As a necessary consequence 

 of such an increase, the sulphur-trioxid content of the ash of the fumi- 

 gated plants would be apt to be higher than that of the ash of the 

 unfumigated plants. 



In the work of Von Schroeder and Schmitz-Dumont, previously 

 mentioned, when different parts of the plants were treated with vary- 

 ing strengths of sulphur dioxid, the sulphur-trioxid content of the 

 treated plants was in excess of that of the control plants in every 

 case, and the percentage of sulphur trioxid in the ash of the treated 

 plants was higher than that in the ash of the control plants. The 

 same Avas found to be true on making analyses of the pines and cow- 

 peas fumigated by the writer.*^ Analyses of fumigated plants grown 



« Haywood, U. S. Dept. Agr., Bureau of Chemistry, Bui. 89, p. 14. 



