218 AGRICULTURAL EXPERIMENT STATION. [Jan. 



The scabby " white" potatoes planted on sections 6, 7 and 

 13 were of a very liglit-skinned sort, much resembling the 

 Gregory, though not certainly of that variety. Those called 

 " black," planted on section 6, were a very few small, 

 elongated, dark-purple tubers, found in the station barn ; 

 the " tops" showed the same dark color which marked the 

 tubers, and produced the only entirely smooth potatoes on the 

 field. The plot was planted May 4, and the first shoots 

 broke through the soil on the 17th. A week later they were 

 well up, and a marked backwardness of sections 1 and 14 

 was observed, as compared with the rest. The retarding 

 effect of planting directly on manure continued to be dis- 

 tinctly noticeable for three weeks longer. Various explana- 

 tions may be offered, however, for this fact, which, by itself, 

 has no special significance. The field was cultivated and 

 hoed at sufficiently frequent intervals, and the plants grew 

 well, l)eing kept fairly free from the potato beetle by two 

 light applications of Paris green, combined with hand- 

 picking. 



On the 4th of June young tubers were found, of the size 

 of a pea, and from this time their size and number rapidly 

 increased. On July 22 the first indications of the rot made 

 their appearance on the leaves of some plants near the south 

 end of the plot, and had soon spread over almost the entire 

 field. As soon as possible, namely, on the 29th of July, the 

 potatoes were dug, in order to avoid the loss of results from 

 the scab experiments to which the rotting of the tubers 

 would lead. The potatoes from each section were kept 

 distinct, and carefully examined with reference to their 

 relative scabbiness. The result in each case is briefiy stated 

 in terms of a scale of five grades, running from " generally 

 smooth "to " very badly scabbed," in the last column of the 

 foregoing table. A compilation of the results there given, 

 with regard to their bearing on the points before indicated, 

 shows that : 1. Deep planting appears to tend to diminish 

 the development of scab, though further experiments in this 

 direction are very desira1)le. 2. While the very dark 

 potatoes were wholly free from scab, little or no difference 

 was to be noticed in the susceptibility of the three light 

 varieties planted ; it is to be regretted that none of the best 



