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commonly found decayed at the heart; and this is very generally the case,even when the exterior circumference of the trunk is in a healthy andvigorous state, and prolific of branches. The most profitable age for fellingthe elm is between 70 and 80 years ; and, if the trunk is disbarked a yearbefore it is cut down, the wood will be more thoroughly seasoned.

Accidents, Diseases, and Insects. The elm is not a brittle tree; and, from thestraightness and strength of its trunk in proportion to its head, it is not liable tobe injured by high winds. It is, however, subject to many diseases; and isvery liable to be attacked by insects. The principal disease with which it isassailed is, a species of ulceration, “ which appears on the body of the tree, atthe height of 3 ft. or 4 ft. from the ground, and which discharges a great quantityof sap. The disease penetrates gradually into the interior of the tree, andcorrupts its substance. Many attempts have been made to cure it in the be-ginning, or to arrest its progress, but hitherto without success. The besttreatment is to pierce the tree to the depth of 2 in. or 3. in. with an auger, inthe very heart of the malady, which is declared by the flowing of the sap.”

(Michx .) The matter discharged by this ulcer has been analysed by M.Vauquelin, and found to contain 0‘340 parts of carbonate and sulphate ofpotash; 0-051 of carbonate of lime ; and 1-004 parts of carbonate of magnesia.(Mem. de I’Institut, tom. ii.) The mode of treatment recommended in the Nou-veau Cours d’Agriculture is, to pierce the ulcer, as above advised by Michaux,and then to dress the wound with powdered charcoal, or a mixture of cow-dungand clay. Elms, when in a soil which does not suit them (viz. when it is eitherexcessively wet, or excessively dry), are very subject to a disease called carci-noma. “ An unusual deposit of cambium takes place between the wood andthe bark : no new wood is formed, but, instead of it, the cambium becomesputrid, and oozes out through the bark,which thus separates from the albumen.”( Lirn/l. Introd. to Bot., p. 298.) This disease shows itself by the extravasatedcambium forming long black streaks down the bark, and by its sweetnessattracting numerous insects, of several tribes, to prey upon it. Mr. Spencethinks that this disease is very probably caused by the scolyti. “ I haveseen,” he says, “many elms pierced by these insects, where the extravasatedcambium partly oozed out in white masses like gum or manna, and partlyformed long black streaks down the hark (as described above), and numerousinsects were attracted to feed on it.”

Many kinds of insects attack the elm. One of these, a species of Haltica(vulgarly called the elm flea, from its habit of leaping), devours the leaves,but is said not to do any serious injury to the tree. (See Ent. Mag., i. p. 427.)It is a beautiful little insect, covered with a brilliant cuirass of green andgold, and having the thighs of its hinder legs so large as to appear almos.tround. These insects are so lively, and so quick in their movements, that,though a branch may appear covered with them one moment, the next theyhave all vanished. The larvae are small and slender, and devour the leavesequally with the perfect insect. (See Diet. Classique d’Hisl. Nat., art.Altise; and Nouv. Cours d'Agric., tom. i. p.256.) In the Dictionnmre decEaux et Forets, and in the Nouveau Du Hamel, it is mentioned that galls,or small bladders, are produced on the leaves of the elm, by the puncture ofsome kind of insect (probably some species of Cynips), which are first green,but afterwards turn black. These galls each contain some drops of a liquid,which is called, according to Du Hamel, elm balm, and was formerly em-ployed for the cure of recent wounds. In the Nouveau Cours d’Agriculture,tour insects that feed on the elm are mentioned. The first is the commoncaterpillar .Bombyx chrysorrhoe'a Fab., which destroys the leaf buds and leavesentirely, so as to give the tree, in spring, the appearance of winter. The second

™ e galeruque de l’orme (Galeruca ulmariensis Fab.), a coleopterous insect,the larvae of which, in some seasons, entirely destroy' the leaves of the elm treesm . public promenades both in England and on the Continent. Mr. Spencementions that, visiting the boulevards at Rouen , in the summer of 1836, he

ound the larvae of this insect had so completely destroyed the leaves of the