50 EXPEEIMENTS WITH REFERENCE TO THE POTATO DISEASE. 



the tops June 18th with i pint of sulphuric acid dihited with 25 

 pints of water. The produce was below the average, but the 

 diseased portion amounted to little more than 5 per cent. 



Charcoal, powdered. — Table I. 19. As soon as the plants 

 were all fairly above ground, powdered charcoal to the amount 

 of 2 lbs. 4 oz., was applied to half a row, being at the rate of 

 1 ton 8 cwt. 72 lbs. to an acre. The soil was removed from 

 the stems to the depth of 2 inches, and as far as 6 inches from 

 each side of the plants. To this extent thecliarcoal was equally 

 scattered, a portion being closely in contact with the stems ; 

 it was then covered with the soil. The produce was below the 

 average, but the portion diseased was little more than 7 per cent., 

 nearly 10 per cent, less than that of the average of rows to 

 which nothing was given. It must, however, be observed that 

 some of tliose rows to which nothing was applied (see Table I. 

 22, 45, and 47) were even less diseased than in this to which 

 the above quantity of charcoal was given. 



Salt. — Table I. 20. Common salt, 2h lbs. to the row, being 

 at the rate of 13 cwt. per acre, was mixed with the soil pre- 

 viously to ^Jlanting. In the experiment with salt, lime, and 

 charcoal, it was remarked that the stems and leaves were of a 

 paler green than those in the adjoining rows where salt had 

 not been applied. The same observation has to be made as 

 regards the colour of the stems and leaves in this experiment ; 

 and the plants also exhibited a somewhat dwarfer habit of growth. 

 The amount of sound produce was at the rate of 1 ton 13 cwt. 

 8] lbs. per acre below the average of those rows to which notliing 

 was applied ; but the quantity diseased was very small, being 

 scarcely 4 percent., and this is less than in any of the returns in 

 Table I., with the exception of the following: — 



Coal-tar sprinkled over the sets. — Table I. 21. In this ex- 

 periment, the sets when placed in the drills were sprinkled 

 with coal-tar by means of twigs, which were dipped in it and 

 shaken over the sets. Of course some would fall on the soil 

 in the drill, as well as on the potato sets. The quantity em- 

 ployed was 1 quart of coal-tar to a row, being at the rate of 

 146 gallons per acre. The stems were somewhat dwarfer than 

 the generality of those in the compartment. The sound pro- 

 duce was 5 tons 17 cwt. 7 lbs. less than that of the average of 

 rows which had nothing. Whether entirely owing to the coal- 

 tar or not, it deserves to be remarked that in this row tiiere was 

 less diseased produce than in any other of which the results are 

 given in Table I., the proportion being only 3/^ per cent. 



Nothing. — Table I. 22. In this row the diseased portion per 

 cent, was little more than one-third of the average quantity in 

 rows which liad nothing. 



