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Gall (Morbid excrescence on the leaf)

a morbid excrescence on the leaf or leaf-bud of any plant, arising probably from the puncture of a cynips.

These small hymenopterous insects deposit their eggs on the leaves, etc., of eaves, of various plants, plants, each species being limited to a single plant, or even a single part of one; thus there is a Cynips ficus caricæ on the common fig, a C. fagi on the beech, and a C. quercus foli on the leaves of the common oak. The so-called oakapples are not fruits but morbid excrescences produced by C. terminalis, called because it deposits its eggs at the extremity of the shoots of the tree. The galls of commerce are produced by the puncture by C. gallæ tinctoria of the leaf-bud of Quercus infectoria, or more rarely of some other species of oak. In the hole made by the insect, an egg is deposited, in due time to be developed into a larva, which eats its way out when it comes to the perfect state. One variety or black. The best galls come from is white or yellow, another green, gray, Smyrna and Aleppo. With the salts of iron they should yield a fine black color, and therefore are used in the manufacture of ink.