84 BRITISH OAK GALLS. 
The scales completely conceal, and effectually shelter, 
the inner pip during its formation. 
This pip, which is the true gall, constitutes the 
nourishment for the larva, and within the tissues it eats 
a cavity, forming the larval chamber. In shape it may 
be pyriform, an elongated oval, or, like a grape-pip. 
The smaller or lower end is truncated or flattened, and 
placed in direct contact with, and affixed to, the axis 
of the bud. The distal end is deeply depressed, 
within which is situated a very small yellowish cone 
having a glossy vertex. At first the colour is pale 
green or greenish-yellow, which, however, soon 
becomes dark green, and later reddish-brown. Early 
in its formation it is soft and sappy, the cell walls thick, 
and easily opened with a finger-nail, later it hardens 
greatly. When nearing maturity numerous (40-50) 
longitudinal striations, which extend from base to sum- 
mit, may be seen on its surface. The average dimen- 
sions are 8 mm. high and 12 mm. at greatest girth. 
The interior is oval, whitish in colour, the larva occupy- 
ing the entire space. 
Until it attams its full growth the gall remains 
firmly fixed, but about the second week in August the 
axis of the bud contracts; the base of the scales thus 
being brought close together press against the lower 
part of the pip, causing it to separate from the axis 
and finally to be pushed upwards until it falls out. 
In Plate XX two strobiles can be seen where the galls 
have reached a position in which a movement of the 
branch will cause them to fall. They were in this 
condition when found by the author. 
During the early formation of the leaf-scales the 
shape of the mass is more or less globular. Three 
types of this form can be seen at d, e in Plate XXI. 
It then emerges into the form of an ellipse or an oval, 
r, a, the central scales soon afterwards pushing their 
way through the distal apex and forming a cone or 
strobile, when the appearance (b) is like that of a 
miniature artichoke, hence one of its popular names. 
