Feb., 1927] PROGRESS OF AGRICULTURAL EXPERIMENTS 



13 



In another experiment Green Mountains, strain H, grown at East 

 Kingston in 1924, were harvested after 90 days, 100 days, 124 days 

 and 148 days. Tlie stock in 1924 was free from mosaic but contained 

 1.37 per cent leaf-rolL The results are given in Table IIIB. 



With Irish Cobblers the data were more conclusive. Irish Cobblers 

 strain E were planted in East Kingston in 1923 and dug after 71 days, 

 82 days, and 92 days. In 1924 the 71-day stockwas harvested after 

 73 and 122 days respectively. In 1924 strain E was planted at East 

 Kingston and harvested after 73 days, 90 days and 122 days. In 

 1925 the results obtained are shown in Table IV. 



Table IV — Effect of earliness of harvest on per cent of leaf-roll and yield of Irish Cobblers 



A study was also made of the effect of temperature on mosaic. Po- 

 tatoes affected with the disease were planted in glazed pots and the 

 water in the soil was kept at 70 per cent of saturation of the air dry 

 soil. The plants were then divided into four series of five pots each, 

 as follows: Series 1, plants exposed to a temperature of 28° C. or 

 above for four hours daily; series 2, plants exposed for two hours 

 daily; series 3, plants exposed for one hour daily; series 4, plants not 

 exposed to a temperature above 25° C. 



The plants were all grown in the same greenhouse except during the 

 period of heating. When the temperature was raised, the plants in 

 Series 4 were removed to a cool greenhouse and those in Series 2 and 

 3 after the required exposure to heat were also removed to the same 

 greenhouse. After the plants in Series 1 had been heated four hours, 

 the greenhouse was rapidly cooled; and when the temperature had 

 fallen to 25° C. the plants in Series 2, 3 and 4 were returned to it. 



