Arthur G. Ruston 401 



(6) 100 viola cuttings taken from plants grown in Roundhay (annual 

 deposit 26 tons per square mjle) were struck in Hunslet, and 98 per cent, 

 grew. 



100 viola cuttings taken from plants grown in Hunslet were struck 

 in Hunslet, but not a single cutting grew. 



It is shown in the smallness and lack of weight of seeds of plants grown 

 in a smoke-infested area. 



Weight of 100 corns of barley grown from same seed. 



It is shown not only in the diminution of the germination capacity, 

 but also in the diminution of the Germination Energy. 



It is shown in the inability of the plant to put up a fight against 

 adverse conditions, as for example, the winter frosts. To test this point 

 nine cabbage plants were planted out in the autumn of 1913 at the five 

 stations mentioned. 



Observation 

 8 out of 9 survived the winter 

 2 out of 9 survived the winter 

 6 dead by Christmas. Frost in February killed rest 

 All dead by middle of November 

 All dead before end of October 



Where the total annual smoke deposit exceeds 100 tons per square 

 mile, it is dangerous to adopt autumn planting either of wallflowers, 

 cabbages or spinach. Where that deposit exceeds 200 tons per square 

 mile it is absolutely fatal. More than 100 wallflowers were planted out 

 in Hunslet in September and not one stood the winter. They can be grown 

 in smoke-polluted districts but they must be planted out in the spring. 



The loss of vitality is shown perhaps most noticeably in the in- 

 hibition of the activity of the various enzymes or ferments which assist 

 in the chemical processes taking place in the plant. The figures given in 

 the following table refer to laurel leaves collected in February, 1913; 

 and illustrate the way in which the activity of the various enzymes are 

 influenced by smoke pollution. 



