11 



is not caused, as has been supposed, by any condition of soil 

 or fertilizers, but by minute parasitic plants belonging to the 

 class known as bacteria. These little plants grow in the super- 

 ficial portions of the tuber, where they act as an irritant, caus- 

 ing a growth of the tissues, which results in the production of 

 the characteristic scab spots. A scabby crop of potatoes 

 results either from the use of scabby seed, or from planting on 

 ground which has previously produced a scabby crop. The 

 germs of the disease live on the harvested potatoes, and also 

 for an indefiuite time in infected soil. When it was found that 

 the scab was caused by bacteria, it readily occurred to experi- 

 menters that corrosive sublimate, a substance extensively used 

 for the destruction of other bacterial germs, might prove useful 

 in treating it. This has been tried, and the corrosive sublimate 

 found to be capable of destroying the germs on scabby seed, so 

 that when the latter was planted on soil itself free from the 

 germs, a smooth crop was produced. 



An experiment in this Hue was tried here last summer. Po- 

 tatoes of the Ueleware variety, very badly scabbed, were used. 

 Previous to planting, half of the potatoes were treated with 

 corrosive sublimate in the following way : Two and one-fourth 

 (2^) ounces of corrosive sublimate were dissolved in two or 

 three gallons of hot water. This was poured into a half barrel 

 and sufficient cold water added to make fifteen gallons in all. 

 The potatoes contained in a coarse "feed" sack were placed in 

 this solution and allowed to remain for an hour and a half. 

 The sack of potatoes w^as then taken out and after draining the 

 potatoes were emptied out and allowed to dry. They were 

 then cut and planted. Treated and untreated seed were planted 

 side by side in alternate plots of two rows each, on land which 

 had not been plowed for many years and was therefore presuma- 

 bly free from scab germs. When the plots were dug the tubers 

 of marketable size were sorted into three grades, viz. : the first, 

 practically free from scab ; second, more or less scabbed ; third, 

 badly scabbed. The following table shows the results: 



