On the Potato Disease. 
leaves on or near the veins, the marks of Avhich might sometimes 
be traced a day or two afterwards ; but I am not aware of any 
extension of the injurj'. 
By some persons, I believe, it has been considered that a pecu- 
liar state of the atmosphere, as regards electricity, had consider- 
able influence in producing the late disease; and, notwithstanding 
conflicting results have been published, both recently and fifty 
years ago, of experiments as to its effect on the growth of plants, 
I cannot come to the conclusion that it is an unimportant agent ; 
for, in the application of so subtle a power, circumstances, witli 
which in the present state of our knowledge we are unacquained, 
might negative the effect of it in one place and not exist at all in 
another. 1 am of opinion, however, that, in the case before us, 
electrical influence was not very considerable. 
I do not consider it necessary to refer to any other causes to 
which this disease has been wrongly attributed ; at any rate not 
in this place ; and I will therefore at once proceed to slate my 
own views of the true cause of the late calamity. 
This I believe to have been no other than Gangrcena vegetabilis, 
or, as it is commonly called, canker, a disease to which I have 
paid some attention for many years past. I may add, that my 
opinion does not at all depend upon the discover}- of this disease in 
the potatoes at Bicton* this year, but arose from a close examina- 
tion of my own last autumn, at which time Dr. Lindley also, 
more than once, pointed out the resemblance of the blotches to 
those of canker,! in the 'Gardener's Chronicle.' It is sufficiently 
known to most persons by its attacks upon fruit-trees; some of 
our most valuable sorts, as the Golden Pippin and Rennet and 
Ribston Pippin, being frequently destroyed by it — I believe, from 
a peculiar delicacy of constitution, which will not endure cold and 
wet situations, but will be perfectly free from it in warmer and 
drier localities : at least, I have found such to be the case with a 
Golden Pippin tree, which while in an unfavourable position was 
literally eaten up with canker, but, having headed it down to the 
stem and removed it to a light dry soil, and a situation much 
warmer than its former one,J; it has stood six years without a single 
blotch of canker upon it, and last year produced a fine crop. On 
the other hand, I have had some sorts, such as the Quarendon, 
planted in the former situation, close to the above, without being 
in the least affected in twenty years, it being more hardy. 
Neither have I ever met with canker in the wild crab, or, to the 
best of my knowledge, in any indigenous plant — if even that be 
* Feb. 21. I- Aug. 23, 30. 
% The leaves and shoots of those vines which ran out into the open 
border were much blotched this year and last, but others growing inside 
were perfectly clear and healthy. 
