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XXXII. — On a Disease in Putatops. By Sir CiiAULiis Lemon, 
Bart., M.P. 
About two vcars ago, I was made acquainted with the fact that 
a (hscaso in field-potatoes cultivated in this neisrhbourhood had 
nianit'cstod itself in a way which threatened to become important, 
and to inllict serious loss on the farmers unless its cause should 
be discovered, and some remedy or prevention devised. It was 
with a view of trying: what could be done in this matter by inquiry 
and by experiment, that I took up the subject ; more in the hope 
of inducing- others to turn their attention to it, than from any con- 
sciousness that I possessed opportunities sufficient to enable me 
to arrive at a very safe conclusion derived fr(mi my own expe- 
rience. And in fact I have obtained no satisfactory result ; so 
that experiments are yet wanting to determine the cause of the 
unnatural growth which I am about to describe. The symptoms 
of the disease are as follows : — The sets appear to sprout as they 
ought, and as others which surround them in the same field have 
done ; but they are stopped short before they reach the surface, 
and no leaves are formed. Large patches in the field are thus 
left bare ; and when the ridges are dug up, ii is found that these 
abortive sets have formed each a little button about two or three 
inches from the surface, and, as it were, gone to rest after the 
effort. The disease produced no very sensible effects on the 
crops till about four or five years asro ; but I have been informed by 
a farmer of this neighbourhood that he recollects a few instances in 
which these litde dwarf^, called by the country people " Bobbin- 
Joans," were noticed as long ago as thirty years. In the neigh- 
bourhood of Penzance, a great potato country, the failure of crop 
from this cause has been more general and more destructive than 
in any part of the country ; in some instances destroying one- 
third of the produce. This information I derive from a gentle- 
man residing there, on whose accuracy I pLice great confidence. 
Without dwelling on the name, then, let us inquire as to the 
thing, " unde derivatur Bobbin-Joan." 
The form in which the question first presents itself is, whether 
the defect is owing to the siiil or the seed ? , Whether, in fact, some 
principle necessary to the growth of perfect potatoes is either 
naturally wanting in the soil, or has been, by excessive culture, 
extracted? And, again, whether the potato may not have con- 
tracted some disease, or perha})s have exhausted that vitality 
which we know will last only a limited time after the creation of 
a new plant from blossom-seed, though its produce may be ex- 
tended over an unlimited surface by the propagation of its off- 
spring. And this latter supposition is that adopted by the gentle- 
YOL. IV. 2 F 
