380 
On the Potato Disease. 
I have omitted mentioning that I tried dipping the diseased 
potatoes in strong solutions, but I found that, in proportion as the 
disease was checked externally, it spread more rapidly within. 
Nothing seems to preserve them better than keeping them dry 
and cool. 
I have at length brought this mysterious subject to a close, and 
hope I have sufficiently explained the nature of the disease and 
such palliative or remedial measures as are really useful ; but 
I have endeavoured to be as concise as possible, knowing that most 
persons have become weary of the subject. Should, however, any 
additional information be required, I shall be happy to afford it 
as far as lies in my power. 
Mai/, 1846. 
Supplementary Observations on the Growth of 1846. 
My ash-leaf potatoes were nearly killed down 1o the ground by 
the spring frosts, but afterwards rallied and looked healthy ; 
they, however, turned off sickly in June (which was very hot) 
without any appearance of mildew, and I found only one diseased 
tuber among them. 
The Shaw, of which I had two acres growing where a potato 
had never grown before, were short in the haulm, and turned off 
by the middle of July, being nearly ripe. The skins were set the 
beginning of August, but, being apprehensive that, after such great 
heat and drought, if heavy rains ensued, they would be attacked 
with last year's disease, I had taken the precaution to pull up the 
haulm (which had several times flagged during ihe intense heat) 
before any mildew appeared, with the exception of a small portion 
for observation. 
I first observed the mildew on the 8th of August. It com- 
menced in the middle of a field of seven acres, on a spot where a 
pit had been filled in with strong clayey loam, the rest of the 
field being a sandy loam. A sort of bowl was formed in this place, 
and the haulm was very luxuriant a few days before, when my women 
complained that they could not get through it to cut down weeds. 
On looking for this spot on the 8th I was startled at the sight of 
a circular patch of blackened stems, the lower parts naked from 
the leaves having fallen from their axils, and the upper part of 
the foliage green and brown, and glittering with the botrytis as 
with frosted silver, the under surface being curled over the upper. 
No microscope was required to discern it tliis year ; it was pei - 
ceptible at a distance of several yards, and continued to spread 
in a circle up the sides of the bowl. I examined the tubers, ai d 
found the greater part of them diseased as far as the pit extended. 
