458 



Remarks on the Poiato-Mtirrain. By W. Wilson, Esq. 



The Warrington Natural History Society having engaged ray ser- 

 vices in the investigation of this subject, 1 am induced to send you a 

 brief statement of the contents of my paper recently delivered to that 

 body, so far as the same may be applicable to the present occasion, 

 when my juincipal design is to discuss the opinions and statements 

 made public by Mr. Stephens, and by tlie Rev. M. J. Berkeley, whose 

 very elaborate essay appears in the ' New Journal of the London Hor- 

 ticultural Society.' 



Mr. Berkeley considers the peculiar characteristic of the potato- 

 murrain is found in the brown spots of the tuber ; and the foetid, pu- 

 trescent state, according to his view, is only the advanced stage of 

 the same disease. My own conclusion is, that these two states have 

 no actual connexion, and may be considered as two distinct diseases. 

 The brown spots are owing to an incrustation of earthy matter, most 

 probably silica, since it resists the action of acids, even when the tis- 

 sue is incinerated. The "dry-rot" of Germany in 1830, 1 consider 

 to have been an aggravated form of the same disease, and as much 

 the opposite of the foetid rot as petrifactioji is the opposite of puire- 

 jaclion. I do not consider it fully proved, as yet, that either of the 

 diseases is necessarily connected with the presence of fungi in the 

 tuber, though 1 admit the fact, that Botrytis infestans was present in 

 those numerous cases which led Mr. Berkeley to state " that in au 

 earlier stage of the disease the Botrytis is uniformly produced," and 

 that one potato, when divided, produced the fungus from every brown 

 speck of the cut surface. The only fungus that I could find in the 

 cellular tissue was Fusarium Solani, and this occurred in one instance 

 only, and not much below the cuticle of the tuber. In all other cases 

 the brown specks had nothing but earthy incrustation. The cells so 

 affected were not emptied of their starch granules, as Mr. Stephens 

 says, nor could 1 perceive any difference in this respect, except that 

 a number of ceils immediately surrounding the brown cells seemed 

 to be empty, no starch having been deposited therein during the 

 growth of the tuber. 



Mr. Berkeley is disposed to support Dr. Morren's opinion that the 

 disease is attributable to the action of Botrytis upon the foliage of 

 the growing potato-plant. It is certainly a very remarkable circum- 

 stance that the fungus should have infested the leaves so extensively, 

 growing out from the interior through the stomata and insinuating 

 the raycelia ihroughout the parenchymatous substance, where the 



