On the Potato Disease. 
489 
opened containing upwards of 40 sacks of potatoes which had 
been grown in exceedingly damp ground : there the disease 
manifested itself to an unmistakeable degree: out of the whole 
40 sacks there were not 5 sacks sound by the beginning of 
February. I likewise observed the same kind of disease in an 
adjoining field * in the year 1829; and my father tells me that 
he has frequently observed it in frames and pits thirty years ago, 
where the heat had suddenly dropped off and the plants had been 
subjected to the drip.f 
I will not attempt to insert a statistical account of the various 
localities where the disease was most severe last year ; be- 
cause il is almost impossible to get at a just estimation. But I 
have invariably found that where the situation was damp and the 
ground rich, the haulm being luxuriant, the crop was most 
affected, except in a few instances where they were planted very 
late and the stalks exceedingly tender ; and in no instance do I 
know that the potatoes were affected last year, where the crop 
was ripe or dug up before the middle of July. 
Taking the above facts into consideration, I must think tha:t 
the breaking out of the disease in the potato crop of 1845 was 
influenced by the continual damp and sunless weather which 
they experienced just at the time that they required a greater 
degree of light and dryness ; but that this ungenial weather, 
in the later part of July and beginning of August, would not 
have had so much effect upon vegetation if it had not been 
forced into rapid and unnatural growth by the excessive heat 
and closeness of the atmosphere in the months of June and 
beginning of July, particularly from the 3rd to the 8th of 
July- 
The disease was simply decay, which began, I believe, in the 
stalks ; yet first showed itself on the leaves of the potatoes 
about the first week in August: it had a dark livid look in spots 
of an oval shape all over the surface of the leaf; a few days after- 
wards it appeared in the axils of the leaves, exactly in the same 
manner as though produced artificially by the drip ; from thence 
* A field called the Rudges, in the parish of Tetbury, at that time partly 
let in allotments for the purpose of growing potatoes. 
t A continual dropping of condensed steam, or water, on one particular 
place. It is customary amongst many gardeners, when the heat of a hot- 
bed suddenly declines, to keep the frame shut close, for the purpose of 
keeping up the requisite temperature of the internal atmo.sphere : whence 
follows an etiolation of the plants; and if a continuance of cold wet 
weather follows, it is almost sure to produce a disease amongst the 
plants, particularly at those spots immediately under where the condensed 
steam collects on the roof, and drops in the shape of a continual dripping 
of water. 
