£08 ON POTATOES. 



conclusion, which I cirew many years ago, is perfectly con- 

 sistent with the opinions i have subsequently entertained, 

 respecting the formation of leaves. I therefore suffered a 

 quantity of potatoes, tlie produce almost whollj^ of diseased 

 plants, to remain in the heap, where they had been preserved 

 during winter, till each tuber had emitted shoots of thriee or 

 four inches long. These were then carefully detached, with 

 their fibrous roots, from the tubers, and were committed to 

 "" the soil ; where having little to subsist upon, except water. 

 Experiment to I concluded the cause of the disease, if it were the too great 

 P~;^\^«^J^;^'^ thickness ^f the sap, would be effectually removed; and I 

 had the satisfaction to observe, that not a single curled leaf 

 was produced ; though more than nine tenths of the plants, 

 which the same identical tubers subsequently produced, 

 i»e re much diseased. 



In the spring of 1808, Sir Johii Sinclair infornied me, 

 tliat a gardener in Scotland, P.lr. Cj-ozer, had discovered a 

 method of preventing the cui-lby taking up the tubers be- 

 fore they are nearly full' grown, jand consequently before 

 they become farinaceous. Mr. 'Cr'ozer, therefore, and my- 

 self appear to have arrived at the same point by very diffe- 

 rent routes; for by taking his potatoes, while immature, 

 Freventionof from the |»arent stems, he probably retained the sap nearly 

 the disease, in' th^'^tate to which my niode of culture reduted' it. I 

 therefore conclude, that the opinions I first formed are welt 

 _i founded; and that the'dlsease may be always removed by 

 the means' I employed, and its return prevented by those 

 aciopted by Mr. Crozer. 



I sent to the Board of Agriculture the substance of the 

 preceding remarks on the origin of the curl, in the year 

 1808; but I do not know whether that account has been 

 published, or not. 



Doivnton, 

 Janvar^ 3lf 1810. 



XI. 



