. Manual of tree diseases . Trees. BODY AND BRANCH DISEASES AND INJURIES 63 trie currents carried by wires is of importance in every city. Any device made of a substance which is a non-conductor (porcelain, or rubber) and which keeps the wires from coming into contact with the limbs, will prevent short circuiting. If the additional injury caused by rubbing is to be avoided, some arrangement must be made for locating the wires so that they are taut and do not come within three or four inches of the limbs. References Stone, G. B. Electrioal injuries to trees. Massachusetts Agr. Exp. Sta. Bui. 15
. Manual of tree diseases . Trees. BODY AND BRANCH DISEASES AND INJURIES 63 trie currents carried by wires is of importance in every city. Any device made of a substance which is a non-conductor (porcelain, or rubber) and which keeps the wires from coming into contact with the limbs, will prevent short circuiting. If the additional injury caused by rubbing is to be avoided, some arrangement must be made for locating the wires so that they are taut and do not come within three or four inches of the limbs. References Stone, G. B. Electrioal injuries to trees. Massachusetts Agr. Exp. Sta. Bui. 156: 1-19, pis. 1-5. 1914. Plummer, Fred G. Lightning in relation to forest fires. U. S. Dept. Agr. Forest Ser. Bui. Ill: 1-39, pis. 1-2, figs. 1-16. 1912. MacDougal, D. T. Effect of lightning on trees. Proe. N. Y. Bot. Gard. 3: 1902. Hartig, R. The effects of lightning. In Text- book of the diseases of trees, pp. 302-304. 1894. Galls Caused by various insects, fungi and bacteria Trees of all kinds often develop large or small galls of various types on the trunk and limbs. The causal agents in many cases have not been studied, but it is supposed that certain insects, fungi and bacteria are frequently responsible for the irritation which results in the overgrowth in the tissue. Mechanical injuries may in some cases also cause galls. The causal agent initiates abnormal division of the cells and the tissues may continue the over-develop- ment for years after the cause is gone. The limb-galls of poplar are known to be caused in some cases by the crown-gall. â Galls on of Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Rankin, W. Howard (William Howard), b. 1888. New York : The Macmillan Company
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