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the diseased portions, and the cells which before contained the fecula 

 are either empty or contain brownish crystalline bodies, which are, I 

 suppose, the remains of the decomposed starch globules. The 

 potato, then, is deprived of its natural principle by this disease, in a 

 manner analogous to the process of germination, in which the starch 

 entirely disappears. 



It is quite certain that the present potato-death is entirely a new 

 plague, as far, at least, as England is concerned ; it is true that some 

 years ago the potato crop was injured by what was called the curl, 

 in which the leaves curled or shrivelled up, but we have no accurate 

 account of this affection, but it was altogether different from the pre- 

 sent visitation. 



What, then, is the immediate cause of the destruction of the potato 

 crop throughout Europe, for all botanists agree in the identity of the 

 disease ? It can only be ascribed, with any degree of probability, to 

 one of two causes, either to atmospheric influences, or to the imme- 

 diate agency of some destroying principle acting directly upon the 

 plants. The latter seems to be most generally received as nearest to 

 truth, and for this reason, that the leaves and stem, and the exterior of 

 the tubers are found to be infested with a mucous fungus, whilst it is 

 likewise stated, on the highest and best authority, that a singular 

 mycetoid production inhabits the intercellular spaces in the diseased 

 tubers. 



I will merely relate the result of my own investigations, leaving it 

 to the Society to receive them or reject them according to their own 

 standard of evidence. I, like all other observers, notice that the leaves 

 in most specimens sent for examination, present a hoariness of aspect, 

 and this hoariness is caused by countless plants of a species of the 

 genus Botrytis, in which I find the stem branches into three divisions. 

 This is the Botrytis infestans, and Mr. Berkeley states in the ' Gar- 

 dener's Chronicle,' he finds this fungus invariably preceding the work 

 of destruction. I likewise find on the black patches of the stem, ano- 

 ther excessively minute fungus, which appears to belong to the genus 

 Fusisporium of Link. It consists of innumerable, excessively minute, 

 elliptic sporidia, collected together in heaps. They exist in countless 

 multitudes, so that the field of the microscope is covered by them. 

 It is utterly impossible to confound these with the sporidia of the 

 Botrytis. These mycetoid plants inhabit the stem, leaves and exterior 

 of the tubers; there is still a most singular mucous fungus, which is 

 described both by Montagne and the Rev. Mr. Berkeley as spreading 

 its mycelia through the intercellular spaces of the tuber itself. Mr. 



