THE EFFECT OF SOOT ON VEGETATION. 



Historical Review 



Various phases of this subject have been studied from 

 time to time by different investigators, the most of whom 

 agree on many of the more important points. The effect 

 of various gases upon plants must be considered in con- 

 nection with the effect of soot because with the soot in 

 smoke there are always associated various gases, as 

 Crowther and Huston (5) have shown. Crocker, Knight 

 and Rose (4, 9, 10, 11) by their several and conjoint inves- 

 tigations and discussions of literature have established be- 

 yond reasonable doubt the high toxicity of certain gases 

 to plants, especially ethylene, and the injury done by 

 greater quantities of other gases. Their first paper deals 

 with illuminating gas and its constituents, while a later 

 paper deals with the effect of smoke, and particularly 

 tobacco smoke, upon etiolated pea seedlings. Although 

 the various responses which they obtained were, for the 

 most part, with etiolated seedlings, yet information con- 

 cerning the effect upon normal plants is not lacking, as 

 is evidenced by the almost complete destruction of certain 

 plants by acute poisoning in a greenhouse during the fumi- 

 gation with tobacco smoke. Buckhout (2) has pointed 

 out the destruction of vegetation in the neighborhood of 

 the chemical works at Natrona, Pennsylvania. This he 

 attributes to the Sulphur trioxide (SOs) and sulphur 

 dioxide (802) fumes. Haywood (8) observed similar 

 effects in the neighborhood about the smelters near Red- 

 ding, California. He went further, however, and obtained 

 evidence bearing on the specific injury suffered by plants 

 from SO2 and SOa fumes. He demonstrated that these 

 gases were responsible for at least a major part of the 

 injury suffered by the plants in the vicinity. Widstoe (S) 

 found that SO2 in small quantities acting for a long time 

 is toxic to plants. Peirce (14) believes that the cement 

 factories in the San Bernardino Valley of Southern Cal- 



