358 
On the Potato Disease. 
of the latter had in the mean time turned yelloWj with brown spots 
on both leaves and stalks, and afterwards died otf black. The 
roots were also decayed. In the garden of a nobleman in War- 
wickshire I also saw a crop grown within the walls, in which I 
could not perceive one unsound tuber, while those of a later sort 
grown in the border outside the walls were badly diseased. 
On the 20th of August I had several roots of Shaw's taken up, 
which I found aftected. The leaves were yellow, and the brou n 
spots upon them spread rapidly, running down the petioles and 
forming circular blotches on the stalks, both above and below the 
point where the petiole was inserted, passing through the inner 
coats of tiie bark and the woody portion into the medulla, the 
structure of which was prematurely broken up at the lower extre- 
mity and stained of a dark colour, but remained for the most part 
healthy and entire towards the tops ; blotches appeared also at 
the base, and on other parts of the stalks, and wherever these 
appeared the bark easily peeled off ; and there were generally two 
or three distinct blotches on a sla]k,*ivith healthy-looking bark 
intervening, sometimes all these united. This crop was taken up 
on the 2yth and 30th of August, at which time I found the tubers 
worse than when I tried them the week before ; some of the roots 
were entirely diseased, others withered and dry, a few apparently 
sound. Many of the potatoes were marked with the too well 
known brown blotches ; some in narrow uneven bands, separated 
by a smaJl portion of sound substance ; others were brown all 
over. The greater number were affected at that point where 
they were attached to the stalks or cords ; these cords were nearly 
all diseased, yet a great many of the potatoes attached to them 
were quite sound. I also observed in some few cases that diseaseil 
potatoes were hanging to cords free from any trace of disease. 
Very frequently the cords broke off about three inches from the 
potatoes, where the disease had been most intense, and remained 
hanging to them. 
I'he only way in which I can account for the entire crop not 
being destroyed is, that at the point of connection of the potato 
with the stalks or cords there is a sort of hylum as between the 
stalk of an apple and the spin* on which it grows; and if the po- 
tato remains until ripe it separates spontaneously at this point, in 
the same manner as fruit. When, however, a fruit-tree is much 
checked in its growth by unusual drought, it is not uncommon for 
the footstalks to shrivel up, and for tl;e fruit to remain hanging in 
its half-grown state to the spur. 1 believe the jjotato received 
just such a check during the hot weather of last autumn, and the 
cords shrivelled up in consequence, and became incapable of trans- 
mitting the mortiierous fluid to the tiibers themselves : thus they 
escaped ; and at the time of digging, as before observed, a very 
