158 
In plants Nos. 2, 4, 6, 12 and 14, the seed tuber was re- 
moved on the dates noted, leaving the tops and roots in 
place as far as possible. Nos. 1, 3, 5, 7, 11, 18 and 18 were 
dug on the dates noted, and the weights of the tops and 
tubers noted. Of all these hills, the dry matter in the seed 
tuber was determined: as soon as the latter was dug. 
Nos. 15, 17 and 19 were examined on J uly 10, but the seed 
tubers were found to be decaying. The remaining hills 
were left undisturbed until the tops had died. 
The column showing the loss of dry matter from the 
. different tubers indicates that the amount of loss was not 
proportional to the time the tuber remained in the soil. 
Neither does it appear to depend much upon the weight of 
the tuber. It should be noted with reference to plant No. 
18, that the tuber appeared slightly shrivelled when dug, 
being different in this respect from any of the others. It 
is possible that it was not in a normal condition. 
It is of interest that the loss in the tubers planted on the 
rich soil is decidedly greater on the same dates than in 
those on the poor soil. From the following table it appears 
that a given loss of dry matter from the tubers in the rich soil 
was accompani d by a much larger development of tops and 
young tubers than the same loss from those in the poor soil. 
Thus in tubers 11, 13 and 18 on the rich soul, and 1, 3 and 
5 on the poor soil, which were dug on corresponding dates, 
if we compute the weight of the tops and young tubers 
that would have been produced at the same rates, by a loss 
of 100 grammes of dry matter from each tuber, we have : 
RICH SOIL, POOR SOIL. 
Tuber No, 11, 1432.2 grammes. Tuber No 1, 466. grammes. 
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It is of interest, also, that the tubers commenced to decay 
first on the rich soil. There is some evidence that decay 
does not take place in healthy planted tubers until the nu- 
triment is entirely exhausted. Thus, tuber No. 6, removed 
from the plant July 22, though apparently entirely sound, 
showed no signs of containing starch ‘when examined 
under the microscope, and only the slightest trace when 
treated with iodine. Tuber No. 7, dug Aug. 2, showed no 
signs of decay except at a single point, where it was 
slightly soft. On cutting it was found to be in a state of 
disintegration in the part near the terminal end. The cen- 
tral portion was of a yellowish transulcent appearance, and 
the cells were largely broken down, yet no offensive odor 
was perceptible. As appears from the table, more than 86 
per cent. of the dry matter had passed out of this tuber. In 
