434 On a Disease in Potatoes. 
to absorb it, the set may be rendered unable to afford the nourish- 
ment requisite for healthy growth. What remains of the original 
substance may be simply transferred to the little tuljer ; as the 
substance of the cotyledons of a bean are transferred to the first 
leaves, before those leaves have begun to perform their functions, 
and attract from the atmosphere the proper nourishment for the 
infant shoot. 
The reasoning which I have thus indulged in, I confess, is not 
conclusive; but it may point the way to some useful and practical 
conclusions ; and I offer it in the hope that the subject may be 
taken up by a more experienced agriculturist. In my hands the 
result pretends to no more than to !)e conjectural ; and my sur- 
mises are as follows : — 
1. That a chemical change may occur in the internal substance 
of a potato ivliich the cije cannot discern, but which may render it 
unfit to afford nourishment to a young plant in the first season of 
its growtli. 
2. That this incipient decomposition may be produced l^y 
dampness, by heating, or by bruises. 
3. That the utmost care is requisite to preserve that portion of 
a crop which it is intended to plant again, in the most ])eri"ect state 
of health and integrity ; without trusting too much to the appear- 
ance of the potatoes which are cut for sets. 
Carclew, Jpril I8ih, 1843. 
P.S. Since writing the above, a circumstance has been related 
to me which at first appeared to be entirely inexplicable ; but, on 
reconsideration, I think it is not at variance with my conjecture. 
A large quantity of ])otatoes were cut for seed : some of these 
were planted in the morning, and some in the evening of the same 
day. Those which were planted in the morning grew well ; those 
planted in the evening produced dwarfs, and ended in a failing 
crop. 
Now I think we have only to suppose that incipient fermentation 
had taken place in the heap of cut potatoes, and the result may be 
thus explained : — The sets which were at the top of the heap were 
sown first, and these would be less affected by the exclusion of 
air and the pressure of the heap. Tliose sown in the evening 
were at the l)ottom of the heap, and may have been bruised by 
the weight of the mass above them. At all events, fermentation 
would commence there, and therefore the chemical change of 
substance which would end in fermentation would commence 
there also. 
