The work was undertaken with the hope of establishing some connexion between the characters of soils as shown by chemical and mechanical analyses, and the quality and composition of the potatoes grown on them. As regards quality, most attention has been given to the occurrence of ‘blackening’ after cooking, especially after a second warming up, and an attempt has been made to get at the cause of this phenomenon. This defect has been often complained of by potato growers and dealers, and seriously affects the price of samples marketed for consumption in towns where the largest buyers are hotels and restaurants which demand a potato capable of keeping its colour after a second steaming. ‘Blackening’ is often associated with sandy soils heavily manured with farmyard dung or town manure, and it has been observed in tubers grown with spring dressings of kainite; concordant opinions, however, are not to be had from practical men, and in fact the defect may arise on the most widely different types of soil. In order to exclude disturbances due to variety, ‘Up to Date,’ as one of the most widely grown sorts, has alone been investigated.