No. 6. 



TJie Disease in Potatoes. 



179 



From the New England Farmer. 

 The Disease in Potatoes. 



Mr. Breck, — Mr. James Brown having- 

 kindly brought me some of the potatoes in- 

 fested with the disease which has this year 

 committed such ravages on t\i\s vegetable, I 

 proceeded at once to investigate the subject. 



The peculiar smell, and the reputed poi 

 sonous qualities of this diseased potatoe, 

 made me nearly certain that it was a species 

 of fungus — a position which I think has been 

 confirmed by my examination with the mi- 

 croscope. 



The appearances which I e.xamined were, 



1st, A nearly black discolouration of the 

 potatoe, just below the skin, penetrating 

 about one-sixteenth to one-quarter of an 

 inch into the substance, and apparently 

 through the skin, in little black, indented 

 tumifications, like pustules. It is probable 

 that in these holes the vegetation of the 

 fungus first begins, and spreads underneath. 



2nd, On the surflice of the skin, where 

 these pustules were enlarged, there had 

 been produced a greyish, slimy substance, of 

 a very offensive smell. 



The black mass, divided in a drop of dis- 

 tilled water, exhibited under the microscope 

 a number of long and oval, very irregularly 

 shaped dark bodies, interspered among the 

 cells of the potatoe. Many of these cells 

 appeared lacerated, but this might partly 

 have been produced by the mechanical ac- 

 tion of dividing, althoug'h I think not alto- 

 gether. The gTeyish slimy mass was semi- 

 transparent and indistinct, when mixed with 

 distilled water, and exposed to the strongest 

 light I could throw. 



In order to discover a remedy for this dis- 

 ease, I decided on applying various sub- 

 stances to this fungus, with a view of effect- 

 ing its decomposition, and examining their 

 action under a microscope. The first appli- 

 cation was salt, and the action of this was 

 60 instantaneous ajid decided, 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 tlien tho- 

 roughly examined. A little salt, on the fine 

 point of a penknife was then added; a nearly 

 instantaneous change took place — the dark- 

 coloured masses separated, much of them 

 seemed to pass away, and instead appeared 

 numerous dark slate-coloured bodies, which 

 I easily recognized as the spores, or repro- 

 ducing bodies of the fungus. With the grey, 

 slimy substance, the effect was still more 

 striking: all the indistinct slime disappeared 

 — the mass becam>e clear and transparent, 

 and left nothing but these innumerable dark 



globules floating about in the drop of water. 

 It seemed to me, that the salt destroyed 

 all the vegetation of the fungus, leaving no- 

 thing but the reproducing spores, which are 

 indestructible by salt. The spores of fungi 

 are the bodies by which they are reproduced 

 and spread, and are analogous to the seeds 

 of other vegetables, and these spores are 

 generated in such enormous quantities, that 

 many fungi, likathis on the potatoe, spread 

 with inconceivable rapidity; but in order to 

 vegetate, they require certain favourable 

 conditions and circumstances, which yet re- 

 quire much investigation. These favourable 

 circumstances are, in my opinion, prevented 

 by salt, as it destroys the fungus vegetation. 

 ThereTore, wherever the disease existed this 

 year, I recommended a liberal supply of salt 

 to be spread on the soil, and trust it will 

 eradicate the evil. It is, at all events, a 

 remedy which cannot do much injury, if it 

 does not succeed. 



During the examination of the black sub- 

 stance, I of ^ourse recognized the grains of 

 starch, which appeared sound; but wishing* 

 to know whether the fungus had affected 

 them, I added a little iodine. The grains 

 immediately took the usual purple colour, 

 and I think were not at all injured; indeed, 

 it appears to me that the injury takes place 

 by the rupturing of the cellular parts of the 

 potatoe. 



I am aware that it requires some practice 

 to judge well of the appearances under the 

 microscope ; but I repeated these examina- 

 tions six or seven times, and always with 

 the same results; still, I should be very glad 

 to have them repeated by others, whether 

 their correctness be confirmed or not. 



My microscope being made by myself, is 

 of course very inferior to those now manu- 

 tactured in London and Paris; and it would 

 be very desirable that some of our scientific 

 societies would import one of these, the cost 

 of which is too high for persons of moderate 

 incomes. It might be made accessible, un- 

 der certain conditions, to those desirous of 

 undertaking such investigations as these; 

 tor there are many cases where the action 

 of various substances on the causes of ani- 

 mal and vegetable disease are examined to 

 very great advantage under the microscope, 

 and effects seen which cannot be observed 

 in any other way. 



Should any gentleman, possessed of one 

 of these superior instruments, be desirous of 

 examining this disease, I would request of 

 him to look at the action of sulphate of iron, 

 sulphate of soda, or of ammiOnia, or of any 

 otiier substance v.hich can be cheaply ap- 

 plied to the soil as a preventive, and to give 

 notice of his observations either in your or 



