Observations upon the Potato Rot. 25 



In an article published by Mr. Teschemacher, in the New 

 England Farmer, about two years since, he attributes the 

 disease in the potato to a fungus, and states, that to discover 

 a remedy for the disease, he apphed various substances to the 

 fungus, to effect its decomposition ; and names salt as the first 

 appUcation. '-The action of this w-as so instantaneous and 

 decided," says he, " that I did not proceed to any other. A 

 portion of the dark substance was placed on a piece of glass 

 on the microscope stand, in a drop of distilled water, and then 

 thoroughly examined : a little salt on the fine point of a pen- 

 knife was then added ; a nearly instantaneous change took 

 place; the dark-colored masses separated, much of them 

 seemed to pass away, and instead appeared numerous dark 

 slate-colored globular bodies, which I easily recognized as the 

 spores or reproducing bodies of the fungus." Having the 

 above article by me at the time I pursued my investigations, 

 I repeated the experiments first tried by him ; but not with 

 similar success. The decomposition of the plant was not 

 effected ; nor was I able to discover the spores. Three seve- 

 ral times I repeated the experiment, but with no different 

 result. I did not try either of the other substances mentioned 

 by him, as time did not permit. 



The disease called in Germany the Potato scab or wart^ 

 and which Dr. Wallworth ascribes to a species of subterra- 

 tiean fungus, which he calls Erysihe subterranea, cannot be 

 the same, I think, as the Potato rot, for this is not caused by 

 a subterranean fungus, but by one which attacks the stalk of 

 the plant, as I have already stated. Mr. Teschemacher, in a 

 subsequent article in the New England FarTner, appears to 

 be of the same opinion, and the remarks which I have offered 

 upon this disease will be found, in the main, to agree with his. 



A writer in Silliman's Journal of Science and Arts, for 

 September, 1845, states that it " cannot be said with certainty 

 that the disease first appears as a fungus upon the leaves ; " 

 and that " there are well authenticated instances where the 

 potato tops have remained green and flourishing, while the 

 tubers were much diseased." In this statement, I am in- 

 clined to think there is an unintentional mistake, which has 

 arisen from want of accuracy in the observations. There 

 may be well authenticated instances of diseased tubers in 



VOL. XIII. NO. I. 4 



