€8 The Potato. 



To do this, it became necessary to ascertain — 



I. Where, and under wliat conditions, the disease fust appeared ; 

 and the period of its first appearance, 



II. What conditions of the atmosphere were favourable for 

 the propagation of the disease, or the converse. 



III. On what portion of the plant did it first appear? 



IV. Could it be artificially induced or prevented, and how? 



V. Did manures in any way affect the propagation of the 

 disease? and, if answered in the affirmative, would the use or 

 employment of any chemical agent alter, check, or remove the 

 disease? 



In reference to No. I., it would appear from the foregoing 

 observations that the disease was due to atmospheric agency \ 

 but the time when it had been first obsei'ved could not — the 

 evidence being so very conflicting — be determined. If men 

 whose accurate habits of observation and strict veracity could be 

 relied on were correct, the disease had appeared in certain localities 

 one or two years before 1845 ; but according to the universal 

 voice it had in that year suddenly appeared in all its malignity. 



II. Atmosphen'c injlnence. — Two or three years elapsed before 

 observations could be made as to what conditions of the 

 atmospliere were favourable to the propagation of the disease, 

 Tiiis portion of Devonshire is remarkably free from fogs ; they 

 very seldom occur, and when they do they fill up the valleys to 

 a ceitriin height, rarely going over the tops of the liills. Ueturn- 

 ing from Okehanipton to Exeter in July, 1848, I noticed on 

 reaching the hill near the three-mile stone on that road that wo 

 were about entering a dense fog, which lay before us white and 

 level. On arriving at the gate of a potato-field — which, being 

 on our light hand, stretched up the hill — a friend who was with 

 me gathered some sticks, and, walking up through the potatoes, 

 came to the edge of the fog, which he marked with the sticks. 

 Ten days after the potatoes below the sticks were a mass ot 

 disease, whilst all above the line icere not affected Jive iceehs after. 



III. Portion of the plant first affected. — It has been asserted 

 over and over again that tlie disease originates in the tuber 

 ])lanted, or in the stem that springs IVom it. That ojiinion is a 

 dclu.'iion. The disease always originates in the leaf, sometimes 

 attacks the stem of the leaf, more rarely still the stem of the plant ; 

 and in the ten.s of thousands oi hmtancefi in which both I myself and 

 the numerous men whom I liave employed in every portion of 

 this county have examined the base of the stem next the portion of 

 the tuber set, no one instance of disease has ever been di.<;covered. 

 Nay, as good potatoes and as free from disease have been 

 obtained, where ])roper precautions have been taken, from 



