415 



that this inference was correct. The identical sample of potatoes 

 which were then free from cryptogamic organisms, now certainly con- 

 tain them. I now find the Arlotrogus hydnosporus, or at least a 

 mucorine fungus according with the description of Montagne, except- 

 ing that in my specimens the spores appear tuberculated or granulat- 

 ed and not bristly, but this may possiblj-^ depend upon age. It 

 inhabits the cavities of the cells, perfecting its spores within them, 

 and I think its creeping filaments perforate the cell-walls. It is pro- 

 per to mention that the same microscopic power has been used in 

 all these observations. In last August, these potatoes, then clearly 

 diseased, contained no fungus ; now being farther advanced in decay 

 they contain it in tolerable abundance. I therefore conclude the Ar- 

 lotrogus is not the cause of the disease which had progressed mate- 

 rially in the tubers before any sign of cryptogamic life was discernible 

 in them. I believe I am therefore justified in expressing my con- 

 firmed opinion that the potato-murrain, at least as far as the destruc- 

 tion of the tubers is concerned, is not produced through the agency 

 of cryptogamic parasites. 



These mucedinous fungi, when present, are very easily seen, and it 

 is quite idle to assert the contrary. I am altogether at a loss to ac- 

 count for the statement of Mr. Phillips (I quote firom a notice in the 

 ' Pictorial Times,' not having seen the original essay), " That no in- 

 sect or fungi can be perceived in the diseased tubers by any means 

 the microscope affords." Either he could not have employed a suffi- 

 ciently high power, or not being a mycologist he must have passed 

 these minute organisms over without recognizing them ; or what is 

 quite possible, the sample of diseased potatoes examined by this gen- 

 tleman happened to be free from them, and he concluded this was 

 invariably the case. But making every allowance, so direct a con- 

 tradiction to the observations of such investigators as Montagne, 

 Berkeley, &c., ought not to have been hazarded on light grounds. 



I am fully aware that filamentous mucedines are generally found 

 in decaying vegetable matter, e. g. apples, &c., but am not so certain 

 that they are invariably present; and to what extent they may be 

 considered as the agents of decay, is a question yet to be solved. I 

 doubt whether their presence in decaying fruits, &c., proves more 

 than the simple fact, that decomposing vegetable matter affords a soil 

 suitable for the nourishment of these cryptogamics. 



Henry Oxley Stephens. 



Old Market Street, Bristol, 

 December 16, 1845. 



