SCIENTIFIC COMMITTEE, MARCH 14. 



xix 



elaborate report, observed that the author had evidently attacked 

 the problem quite in the right way, by experimenting on plants 

 with the separate ingredients of urban fogs ; and that, as the 

 report showed, the investigation had raised a number of inter- 

 esting and very important questions in vegetable physiology. It 

 was, indeed, a matter of surprise to see how much information 

 Prof. Oliver had extracted from his investigations in the short 

 time at his disposal. He trusted that the author would persevere 

 with his experiments, as he would have the hearty sympathy of 

 everyone interested in the subject. Prof. Ward alluded to some 

 old experiments of his own in which he found that in fine, dry, 

 bright, and sunshiny weather plants resisted the effects of 

 sulphurous acid better than in dull seasons, thus correlating in 

 an interesting manner the results of Prof. Oliver, in that in 

 foggy weather sulphurous acid gas was most effective in injuring 

 plants. The result of this action was a plasmolysis and diffusion 

 giving the appearance of " sweating " in the cells. The sul- 

 phurous acid in the gaseous condition penetrated the intercellular 

 spaces of the tissues, and entered the cells in solution. 



Dr. Miiller called attention to the statement in the report 

 that, according to Dr. Bailey, the organic matter which forms 

 a large proportion of the greasy deposit left by fog, and which 

 proved so injurious to plants, consisted mainly of some form of 

 pyridine. Now, considering that pyridine is a rather volatile 

 liquid substance, this is a somewhat surprising fact, and the 

 question arises how the pyridine and other similar volatile con- 

 stituents of smoke become thus fixed and precipitated. He 

 suggested that this probably is brought about by the agency of 

 the particles of solid hydrocarbon and tarry ingredients of the 

 fog, which possess great affinity for these volatile substances 

 and absorb them. It is now well understood that these solid 

 constituents of the smoke, along with the mineral dust suspended 

 in the atmosphere, form the primary cause of the formation of 

 fog. 



Dr. Masters exhibited sprays of Holly, Skimmia, and Aucuba 

 covered with sooty deposit of fog, but yet the foliage was 

 apparently healthy. He attributed their capability of resisting 

 the deleterious influences to the great thickness of the cuticle 

 possessed by these plants. He observed that evergreens often 

 possessed in addition two or three rows of palisade cells, instead 



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