On the Potato Disease. 
385 
bug Lygus, first noticed by Mr. Balkwill, who said the disease was 
caused by tlie acrid fluid discharged by it. I squeezed this fluid 
oil some leaves of the phuit in my vinery, and tlic mark is visible 
still (Oct. 10), but it never extended farther. I also caught a great 
quantity of the Altica exoleta? on the leaves, which they nibbled 
into innumerable holes. I found also the red spider in some 
places feeding on the under surface, and causing the leaf to 
assume a wliitish appearance, as it does in cucumber and melon 
plants. I placed all these species upon the potato-plants in 
my vinery, but, with the exception of the inoculated leaves, 
they are perfectly healthy now (two months since, October 14). 
On the 23rd of July, however, I found a plant in my field, 
two or three of the lower leaves of which were rather sickly, 
and, when taken up, it had one diseased tuber attached to it. 
The specks which I have alluded to as being white on the 
skin of the healthy tuber were in this brown and filled with 
putrid matter, which, when removed, left a small hollow like 
a cup : the corrupt fluid exuding from each of these cups or 
glands (as I suppose them to be), it becomes the nidus for 
a tuft of mildew. Not seeing cause enough to account for this 
diseased tuber, I split the undergound stem, when I found in the 
inside the larva of the Molobrus (bred from diseased potatoes last 
year, and figured by Mr. Curtis in the ' Gardener's Chronicle'), 
as shown in the drawing I have made; but whether this small 
B 
1. Underground stem of potato, pcrforatod and partly eaten by the larva of a lly, 
Molobrus fucatus ; bred by Mr, Curtis amongst diseased potatoes — tlio stem 
diseased, as also the lower roots — folia;^e sickly. July 23. 
2. Diseased potato attached to the above stem, at the -\- the cord rusty-brown. 
3. The larva magnified. 
maggot had promoted the disease in the tuber or not is more than 
I can say ; but 1 think not, for the following reason : — I had a 
piece of potatoes, with oats on each side, which 1 feared the wire- 
worm would have entirely destroyed. Suddenly, however, they 
recovered, and soon after many of the potatoes began to flag and 
