1 64 On the Prevention of Curl and Dry- Rot in Potatoes. 
plague. The explanation of the rule and of this exception to it 
appears to me to be as follows: — Curled potatoes ripen early, 
some weeks before the healthy plants, and consequently are almost 
always too ripe when taken up to make good sets, and if so used 
the disease will rapidly increase each succ essive season. In this 
instance, however, the infected potatoes were taken up before they 
were ripe, and proved to be as good sets as could be used. To 
proceed. The potatoes above-mentioned were taken up the 
second w-eek in November, 1841. Having been planted so late, 
the round reds were not ripe ; the black kidneys, a much earlier 
variety, were. 
1842. — These potatoes were used for seed in 1842. The 
unripe reds produced an excellent crop, without, as far as I am 
aware, a single failing plant. The ripe black kidneys were again 
a failing crop. In the middle of May of this year (1842) I 
planted with these black kidneys a small piece of old grass-land, 
as a preparation for forest- trees. This plot of ground had been 
from time immemorial flowed over by the waste water from an 
old and ill-constructed farm-yard immediately adjoining, and was 
therefore as rich as could well be imagined. The potatoes had 
immense tops, but very small tubers ; and, when boiled, the 
favourite black kidneys seemed quite to have changed their cha- 
racter. Instead of the firm mealiness for which they are remark- 
able, they now bore much more resemblance to a piece of yellow 
soap. They also continued growing till the frost and snow made 
it dangerous to leave them any longer in the ground, and they 
were taken up still thoroughly unripe. The round reds, grown 
on old-going land, were taken up ordinarily ripe, and were mealy 
and good. 
1843. — In 1843 these two kinds were again used for seed, 
and the ripe reds had numerous failures, but the unripe black 
kidneys were as even and vigorous a crop as could be wished. 
I had not yet learnt to attribute the failure to its right cause, and 
was accordingly much puzzled to account for the curl among the 
round reds, which had thriven so well the two previous seasons. 
I was absent on the Continent during the autumn of 1843; »but 
my bailiff informed me that, in consequence of a heavy fall of 
snow in October, he took up the potatoes earlier than he intended, 
and that the red potatoes were not ripe, but that the black kidneys 
(a capital crop) were. 
1844. — It was not till the spring of 1844 that I became con- 
vinced thai the maturity of the potato intended for seed mate- 
rially affected the vigour of the future j)lant ; and the crop of 
that year furnished me with some facts strongly corroborative of 
tliis opinion. The ripe black kidneys again failed to a great 
extent : not less, I think, than half the sets perished without 
