372 
On the Potato Disease. 
the temperature was then 40", it behig usually 44° while the plant 
was there. On the 2nd of April I brought it up, when the only 
apparent difference in it was, that it was not of so dark green a 
colour as when I placed it there. Still it was by no means etio- 
lated. I at once set it in the sun, which was then bright, and at 
five o'clock P.M. hrown spots appeared on three of the leaves.* I 
continued to set it out by day, although the weather became dull, 
and protected it in a cool pit at night. On the 6tli of April 
nearly all the leaves were blotched, more or less ; but, although I 
examined every one separately with a Stanhope lens, I found no 
mildew on any one. On the 20th of April several petioles doubled 
doion^ at the places where blotches had formed, and the upper 
parts SWUNG backwards and forwards in the air, as I remem- 
ber to have seen them last year ; and on one withered spot there 
was a species of mildew (fig. 6. d.). On the 30th of April only 
two leaves at the top were free from blotches, and several of 
THESE HAD FORMED ON THE STALKS. I Subjected another plant 
to similar treatment a short lime afterwards, and the result 
WAS THE SAME ; the figure (e) being composed of stalks and 
foliage from both plants, as seen May 1 6th. I afterwards took 
another victim, which is now (May 23rd) in a progressive state 
of decline. The two former plants were turned out of the pots on 
the 29th of May, in the presence of a gentleman to whom I have 
before referred, but none of the potatoes were diseased, although 
the roots of one plant were quite withered. The other had not 
become diseased down to the roots. My own opinion, however, 
remains the same. One of the most eminent botanists in the 
kingdom, to whom I communicated my experiments, also con- 
curred in my views as to the nature of the disease ; and assured 
me that he did not consider that this at all invalidated them — as,, 
however near I might come, it was almost impossible, in such an 
experiment, so to control the elements as to render circumstances 
exactly alike, and that the blotches on the haulm alone proved 
the identity of the disease. Being in a pot might make some dif- 
ference. Many plants last year had no diseased tubers, although 
badly diseased in the haulm. Every other plant in my vinery 
continued in perfect health, except two, which I shall mention 
presently. On the 20th of April a sharp frost cut the forward 
potatoes out of doors, and, early in the morning of the 21st, drops 
of brown fluid were resting on the leaves, very similar to that seen 
in diseased potatoes, I plucked some of these leaves, and inserted 
part of one of them under the bark of a potato-stalk in my vinery. 
This has produced a large blotch quite round the stalk, and 
SPOTS ON THE LEAVES ALSO, whicli will iu a few days destroy the 
* Vide specimens. 
t Vide fig. K. 
