CHAP. CI. ULMA‘CEX. WU LMUS. 1385 
commonly found decayed at the heart; and this is very gencrally the case, 
even when the exterior circumference of the trunk is in a healthy and 
vigorous state, and prolific of branches. The most profitable age for felling 
the elm is between 70 and 80 years; and, if the trunk is disbarked a year 
before it is cut down, the wood will be more thoroughly seasoned. 
Accidents, Diseases, and Insects. The elm is not a brittle tree; and, from the 
straightness and strength of its trunk in proportion to its head, it is not liable to 
be injured by high winds. It is, however, subject to many diseases; and is 
very liable to be attacked by insects. The principal disease with which it is 
assailed is, a species of ulceration, “which appears on the body of the tree, at 
the height of 3 ft. or 4 ft. from the ground, and which discharges a great quantity 
of sap. The disease penetrates gradually into the interior of the tree, and 
corrupts its substance. Many attempts have been made to cure it in the be- 
ginning, or to arrest its progress, but hitherto without success. The best 
treatment is $0 pierce the tree to the depth of 2 in. or 3. in. with an auger, in 
the 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 of 
potash ; 0°051 of carbonate of lime ; and 1°004 parts of carbonate of magnesia. 
(Mem. de ? 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-dung 
and clay. Elms, when in a soil which does not suit them (viz. when it is either 
excessively wet, or excessively dry), are very subject to a disease called carci- 
noma. An unusual deposit of cambium takes place between the wood and 
the bark : no new wood is formed, but, instead of it, the cambium becomes 
putrid, and oozes out through the bark, which thus separates from the albumen.” 
(Lindl. Introd. to Bot., p. 298.) This disease shows itself by the extravasated 
cambium forming long black streaks down the bark, and by its sweetness 
attracting numerous insects, of several tribes, to prey upon it. Mr. Spence 
thinks that this disease is very probably caused by the scolyti. “I have 
seen,” he says, “many elms pierced by these insects, where the extravasated 
cambium partly oozed out in white masses like gum or manna, and partly 
formed long black streaks down the bark (as described above), and numerous 
insects 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 anc 
gold, and having the thighs of its hinder legs so large as to appear almost 
round. These insects are so lively, and so quick in their movements, that, 
though a branch may appear covered with them one moment, the next they 
have all vanished. The larvae are small and slender, and devour the leaves 
equally with the perfect insect. (See Dict. Classique d’ Hist. Nat., art. 
Altise; and Nouv. Cours d Agric., tom.i. p. 256.) In the Dictionnaire des 
Eaux et Foréts, 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 of 
some 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 Cowrs d Agriculture, 
four insects that feed on the elm are mentioned. The first is the common 
caterpillar Bombyx chrysorrhee‘a Fab., which destroys the leaf buds and leaves 
entirely, so as to give the tree, in spring, the appearance of winter. The second 
is the galeruque de l’orme (Galerica ulmariénsis F'ad.), a coleopterous insect, 
the larvae of which, in some seasons, entirely destroy the leaves of the elm trees 
in the public promenades both in England and on the Continent. Mr. Spence 
mentions that, visiting the boulevards at Rouen, in the summer of 1836, he 
found the larve of this insect had so completely destroyed the leaves of the 
