ROSE-GALLS . 
305 
the use of the knife. There are about thirty-five of these 
wooden knobs. 
On selecting one of the knobs, and examining it, a few very 
small circular holes are seen, showing that the insects have 
made their escape from the cells. Indeed, one or two of the 
insects were found entangled amid the dry and crisp hairs that 
surrounded the gall, and thus formed a second barrier, which 
they could not penetrate. When, however, a sharp knife is 
carefully used, the woody tubercle can be laid open in several 
directions, and then proves to be a congeries of cells fused 
together into one mass, and varying from four to twenty in 
number, according to the size of the insect. Perhaps, on an 
average, ten cells may be reckoned in each knob. 
The cells are of different sizes, some being more than ten 
times as large as others. The superior dimensions of the cell 
seem to be obtained at the expense of the walls, so that the 
large cells can be broken by the finger and thumb, while the 
small cells cannot be opened without the knife. 
The insects themselves are equally variable, some being mere 
dots of shining blue and green, while others are about as large 
as the common red ant of the garden, but with plumper bodies. 
In consequence of these two facts, the large, strong-jawed insect 
can easily make its way through the comparatively thin walls of 
the large cell in which it was enclosed, while the small and 
necessarily weak-jawed specimens are utterly unable to pierce 
the walls of their cells, which are so thick that they must bore 
a hole equal in length to that of their whole body before they 
can escape into the air. Consequently, the great mass of the 
insects that are found in the cells are the small specimens, the 
larger having made their escape. I find that on an average 
twenty small insects are thus found in proportion to one of the 
larger kind. 
There is another gall, very common in England, which is 
found upon the oak, and which is generally thought, by persons 
who are unacquainted with botany or entomology, to be the 
bud which naturally grows upon the tree. 
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