On the Potato Disease. 
373 
K. 
Ash-leaf potato (trial plant), drawn May 14, 1846. X Monilia racemo^a. 
plant* I have since tried it on another, and this is also working 
in the same manner. This experiment I consider most important^ 
for it not only shows that cold suddenly succeeded by bright sun 
(as it was between six and seven o'clock on the morning of the 
21st of April) will convert the sap from its natural colour to 
brown, but, from its having acquired thereby a phagedenic pro- 
perty, it also points to the same causes as the origin of canker, and 
thus confirms the view which I have taken of it in a former part 
of this essay. 
It also proves the correctness of its analogy with the effect on 
frozen limbs as mentioned by Darwin. And does it not also 
show that canker is neither more nor less than the mortiferous 
principle of the vegetable system, as the true gangrene is of the 
animal ? For, if either is arrested before it has entered into the 
general circulation, both animal and plant may be saved, but, if 
allowed to extend into the more vital parts of either/j- death is 
* This plant was sent to the R: A. Society's Rooms, where it died in a 
few days. 
t I saved several bunches of grapes last year by cutting out the blotches 
on the stalks as soon as they appeared. 
