GALL, in natural history, denotes any protuberance or tumour, produced by the puncture of insects on plants and trees of different kinds. Galls are of various forms and sizes, and no less different with regard to their internal structure. Some have only one cavity, and others a number of small cells communicating with each other, or entirely separate ; some of them are as hard as the wood of the tree they grow on, whilst others are soft and spongy ; the first being term ed gall-nuts, and the latter berry-galls, or The general history of galls is this : an insect of the fly-kind (see Cvxirs), is in structed by nature to take care for the safety of her young, by lodging her eggs in a woody substance, where they will be defended from all injuries, and be able to procure a sufficiency of nutriment, proper for them, consisting of the juices of the plant upot which they are placed: she for this purpose wounds the branches or leaVes of a tree, and the lacerated vessels, discharging their contents, soon form tumours about the holes thus made. These tumours are gradually increased to their full size by the morbid action of the vessels of the plant, occasioned by the continual and peculiar stimulus of the included infant cynips : and, although their variety is very great, of form, size, colour, and consistence, it is no difficult matter for the practised eye to deter mine the species of cynips by the appear ance of its gall. The hole in each of these
tumours, through which the fly, when arrived at perfection, has made its way, may for the most part be found ; and when it is not, the maggot-inhabitant, or its remains, are sure to be found with in, on breaking the gall. It is to be ob served, however, that in those galls which contain several cells, there may be in sects found in some of them,though there is a hole by which the inhabitant of an. other cell has escaped. Oak-galls, put in a very small quantity into a solution of vitriol in water, though but a very weak one, gives it a purple or vitriol colour, which as, it grows stronger becomes black ; and on this property depends the art of making our writing-ink, as also a great deal of those of dyeing and dress ing leather, and other manufactures. See Dig, etc.