292 Journal of Agricultural Research voi. xvi, no. h 



WISCONSIN PEARiv (table; I, a-b) 



Aggregation Table I, A, illustrates the performance of the certified 

 Wisconsin Pearls potatoes in 191 6. There was a total of 774 seed pieces 

 planted, the result of dividing 387 tubers. The striking thing to be 

 noted in this section of the table is the fact that with the majority of 

 diseased plants in either row the twin was healthy. In only 1 1 cases did 

 both twins fall outside of a healthy square, five of these being in the 

 square 00. If vascular infection was to act here only the 5 twins in the 

 00 square could properly be said to come under control of it, because it is 

 the only instance where the performance was the same for both twins. 

 In the cases of the 80 pairs of twins, i of which was in some way diseased 

 and the other healthy — that is, those in both rows where i twin was 

 an H plant, exclusive of those in HH — it must be regarded that the 

 disease was newly contracted. Before planting, all tubers were cut at the 

 stem end to inspect for vascular discoloration, indicating the presence 

 of a possible disease organism. Cultures were made from diseased 

 tissue. Only 27 tubers, or 6.98 per cent, showed any discoloration. 

 Tabulating then according to the place the tuber occupies in Table I, A, 

 their places are shown in Table I, B. 



According to the old conception of the danger of planting diseased seed, 

 the 27 tubers, planting the 54 plants here shown should have given some 

 sign of disease. The 2 which fall without the HH square are healthy 

 plants, for one-half of the tuber would indicate no tendency to disease be- 

 cause of the vascular parasite, but because field conditions acted as in 

 the case of 78 similarly situated plants, as shown in Table I, A. 



WISCONSIN RURAL (TABLE I, C-D) 



The certified Wisconsin Rural potatoes were treated in the same manner 

 throughout, and were tabulated in the same way: 444 tubers were used, 

 planting 888 hills, and their performance is shown in Table I, G. 



The plants in this table are well distributed except in the HD columns. 

 The performance of the twins as representing the strictly inherent ten- 

 dencies of the tuber seems not to be indicative of any considerable failure 

 because of previous faults. There are 40 pairs in 00, and 30 and 67 

 pairs in HO and OH, respectively. The factors which placed the 40 

 pairs in 00 did not act on them as parts of 40 tubers, but as 80 individual 

 plants, the same as took place with the 30 and 67 pairs, one-half of which 

 were healthy. This variety is peculiar in showing such a contrast be- 

 tween susceptibility to disease and vigor to survive and grow away from it. 

 The tubers of this lot were planted within 10 feet of the lot represented 

 in Table I, A. 



Table I, D, represents the place in which those seed tubers fell which 

 showed discoloration in the vascular system. These 16 tubers (3.60 -f- 



