ON THE EFFECTS OF URBAN FOG UPON CULTIVATED PLANTS. 53 



If we could eliminate atmospheric contamination, I do not 

 think the reduction of light alone would be a very serious cause 

 of complaint. Now and then it might be so to some extent, though 

 it would hardly be a grievance of the first magnitude. It is 

 when we have superadded aerial contamination that the mischief 

 is done. Many very common injuries to flowers — injuries which 

 impress the cultivator and catch his attention — have no causal 

 relation with diminished illumination. The inflorescences of 

 Rhododendrons, which become so characteristically glued up in 

 their bud-scales and fail to open, will expand perfectly in total 

 darkness. So also will the flower-buds of most Orchids. Since, 

 however, the application of artificial light, in a manner likely to 

 be effective, would be an unduly heavy burden on the grower, 

 we will dismiss this aspect of the question, and proceed to discuss 

 whether atmospheric contamination can be cheaply remedied. 



And, first of all, can fog be neutralised or absorbed after it has 

 entered a plant-house ? I have experimented with several things, 

 but my results do not justify me in basing any recommendations 

 upon them. The sluicing or syringing of liquid chemicals about 

 a house has little to recommend it, even when attended with 

 some success. To solids the objection is not so great. But 

 I have not found that carbonate of ammonia, for instance, exerts 

 any noticeably beneficial action as a neutraliser of the acid vapour 

 of fog. But fog is a complex product, and anything which might 

 neutralise one constituent would probably leave the others free to 

 do their damage. I have never felt that anything could be done 

 inside the house towards mitigating fog except the taking of certain 

 precautions as regards watering and heating. And I am of this 

 opinion still. 



The scope of this report does not extend to a discussion of 

 the big question of the abolition of fog. Even the most sanguine 

 of the present generation can hardly hope to enjoy any abatement 

 of the fog-nuisance. So that I shall be more practically dis- 

 charging my mission in discussing how fogs may be excluded 

 from plant-houses than in attacking the greater problem. Stoves, 

 within certain limits, can be covered in with sheets of canvas, and 

 this has been tried with encouraging results. I first heard of 

 this method being systematically and successfully applied from 

 Mr. C. Davies, of the Mote Park Gardens, Maidstone. Even the 

 fogs of limited duration which are experienced there are sufficient 



