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a cavity formed in the trunk by the destruction of the internal tissues. The formation of tree hollows is usually the result of the vital activity of several species of saprophytic fungi and bacteria, often with the aid of ants and birds (woodpeckers).
Hollows occur most often in the trunks of old trees, and they develop slowly. Mammals, birds, and insects often live in hollows. Trees with hollows grow poorly and later die because they lose their solidity and are easily broken by wind. If trees with hollows are treated in time, the life of the tree may be prolonged. Treatment consists of the removal of all decayed tissue from the cavity; when the walls have been scraped down to the healthy wood, they are disinfected with 1 percent solution of Formalin or mercuric chloride or with a 3-5 percent solution of iron or copper vitriol and covered with an insulating coating. Small tree hollows are then sealed with wood plugs and large ones with a mixture of clay, sand, and rubble, after which they are covered with cement. In many tree varieties, hollows are treated in autumn, but birches, maples, and poplars are treated from the end of May until July because the early spring flow of sap destroys the insulation coating.
V. A. KOLESNIKOV