. Bulletin - Massachusetts Agricultural Experiment Station. Agriculture. FiG. 51. —Chestnut tree cavity resulting from stump growth, with cavity covering of cement about 6 inches thick. (See ) has a tendency to displace the tacks; consequently the metal covering becomes loose and valueless in a short time. Metal is inclined to deteri- orate in a few years, and cannot accommodate itself to much movement in the tree unless it is used in sections and imbricated or overlapped like shingles. Sometimes metal is used to cover cement-filled cavities, but this is of no particular value, and does
. Bulletin - Massachusetts Agricultural Experiment Station. Agriculture. FiG. 51. —Chestnut tree cavity resulting from stump growth, with cavity covering of cement about 6 inches thick. (See ) has a tendency to displace the tacks; consequently the metal covering becomes loose and valueless in a short time. Metal is inclined to deteri- orate in a few years, and cannot accommodate itself to much movement in the tree unless it is used in sections and imbricated or overlapped like shingles. Sometimes metal is used to cover cement-filled cavities, but this is of no particular value, and does not improve the appearance of the tree. The principal pur- pose in using it over cement is to cover the cracks, and when used in connection with iron bands over the surface it is supposed to help hold the cement in place. In some cases where metal is used in this way it is lapped over on the bark 4 or 5 inches, but this destroys the underlying tissues and arrests their future develop- ment, thus defeating one of the main objects of treating cavities, — , encouraging and directing the healing tissue or callus formation. Elastic Cement. — Elastic cement, such as is employed by slaters, has been used for some years in tree repair work, and was recommended for this pur- pose by the Massachusetts Forestry Associ- ation about 1900. Its principal value in tree repair work consists in its elastic properties and its adaptability to places where there is considerable movement. It is too expensive for use in large cavities, costing from 4 to 15 cents per pound, but it has been employed to some extent for filling small spaces and also as a thin covering for cavity openings. In the latter case wire mesh is strung across the cavity opening, the wire mesh being re-enforced with iron and shaped to conform to the outer contour of the tree; and the elastic cement is plastered on the mesh. (See Figs. 54 and 55.) This method of treating cavities has been especially recommended by Mr. L.
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