396 



Plant as an Index of Smoke Pollution 



Pyrethrum, June 28th, 1914. 



Direct tintometer readings 



Annual 

 District deposit 



Weetwood Lane 42 

 University 1 14 



Hunslet 539 



Red 

 38-6 

 30-0 

 26-0 



Blue 

 3.8 

 2-8 

 1-5 



Total colour 

 Yellow units 



42-4 

 32-8 

 27-5 



Lupins, June 18th, 1918. 



Direct tintometer readings 



District 

 Hunslet 



Growth 



1 year 



2 years 



3 years 



Red 



100 



7-6 



4-4 



Blue 



10-2 



5-0 



3-2 



Yellow 

 

 

 



Total colour 

 readings 



20-2 



12-6 



7-6 



The first one shows the tendency of all bronze flowers in a smoke- 

 infested district to run to yellow; the second shows the cutting down of 

 the red and blue tints and the third illustrates the fact that the longer 

 a plant remains in a smoky atmosphere the more it loses the power of 

 producing colour; evidently it is not simply a case of mere bleaching, 

 but a radical change in the constitution of the plant. 



We may notice casually the fact that smoke pollution means stunted 

 growth, but we may get a measure both in the laboratory and in situ 

 of the growth of plants, where the conditions other than atmospheric 

 conditions are the same; and the relative growth will be found to be 

 roughly inversely proportional to the smoke pollution. In the laboratory 

 the relative growth has been measured by estimating the amount of 

 carbon dioxide assimilated by a unit area of leaf in a unit of time. The 

 following results refer to experiments made with laurel leaves of the 

 current year's growth taken from shrubs grown in the districts men- 

 tioned. 



In situ the relative growth of plants in different districts has been 

 compared, by filling large wooden buckets with soil taken from the same 

 field in the country, sinking the buckets in gardens in different parts of 



