British oak galls / by Edward T. Connold.

  • Edward Thomas Connold
Date:
1908
Catalogue details

Licence: In copyright

Credit: British oak galls / by Edward T. Connold. Source: Wellcome Collection.

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    stubs as on young and old trees. The leaf is consider- ably distorted by the growth of the gall, and fre- quently the material which would have formed a leaf is almost absorbed in the formation of the gall, a small portion only developing to form a ridge or frill upon the surface. Under such conditions of growth the gall-mass is usually more or less globular, but when situated upon the blade of the leaf the shape is very irregular, although the bulk may not be more than normal. A solitary mature globular specimen on the end of a twig, having little or no leaf membrane attached, has the appearance of a small gall of Gtjnijps Kollari. Growth is rapid, and during the early part of the time the gall is solid and firm, although somewhat succulent, and it extends in equal, or nearly equal, proportions on both surfaces of the leaf. As maturity approaches a large cavity is formed, within which is the inner gall; a small, reddish-brown larval cell, ovoid in shape, loosely adherent, with very thin walls, and about 2 mm. in its long axis, occasionally with a minute papilla at one end. Two, three, and sometimes four galls will anastomose, and upon cutting the mass open it will be seen that the inner galls are in some cases separated by very thin septa, or the cavity remains undivided. When gall growth takes place at the base of a petiole the whole of the petiole is involved and a con- siderable swelling results. When situated at the extremity of a twig, and small portions of leaves develop upon the gall structure, there is a close resemblance to a gall of A. wflator. It is extremely abundant on some trees, affecting mostly the small twigs springing from the trunk, where not infrequently almost every leaf is galled. It may also be found in great plenty on bushes and very young trees. Apparently it occurs but rarely on the higher boughs of old trees. Some of the imagines of Aphilothrix collaris emerge
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