Gum-Secretion, in horticulture, is a kind of gangrene, or morbid production of gummy matter, exuding from the wounded alburnum or sap-wood of deciduous trees, whether the injury be caused by internal disease, or by external violence, as is the case in canker.

Cherry and other stone-fruit trees are particularly affected with this exudation of gum, which, however, concretes in dry weather, and thus its farther discharge is prevented: otherwise the free would weep, and perish from a deficiency: of nourishment.

Dr. Darwin conjectures this gummy substance to be part of the nutritious fluid designed for the new buds, which are usually form-ed in the summer. He proposes to obviate its exudation, by fastening a thin plate of lead on the part af-fected, which is previously made smooth with a knife, so that no rain or dew can penetrate : a piece of sponge, soft leather, or India rubber, might be bound on the tree beneath the lead, till the wound is healed. - The Doctor suggests another method of closing the wound ; namely, to cut out a piece of bark from a tree of inferior value, but similar nature; to adapt it to the wounded part, after its edges are nicely smoothed, and to tie it on with list, flannel, or other bandage; in order that its elasticity may secure a continual pressure, without injuring the bark.

Mr. Bucknall, who has made some ingenious observations on the formation of gum, in the 12th vol. of the "Trar:saciio?is of the Society for the Encouragement of Arts," etc. disapproves of smearing the diseased tree with tar, or any other sub-stance that may impede the proper circulation and perspiration of the juices, as it must necessarily hurt the tree. The best remedy, in his opinion, is the medication (see vol.i. p. 432) ; for, being applied simply like a plaster, and not being extended farther than is required by the bare wood or torn bark where the gum oozes forth, it is not attended with those unfavourable effects. He. farther assures the Society, that in each of these cases, "the medication becomes supremely salutary," on account of its drying qualities ; for the wounds heal in one half of the time they would close, when exposed to heat, cold, moisture, and vermin.

Gum, or Gum-Secretion, a disease in trees, arising from various causes, but mostly from injudicious pruning ; bruises, or injuries committed on the wood, or bark, by the hammer in nailing the branches against walls ; pinching the shoots by making the trellises too tight, or by driving the nails too closely to the branches. It may also be occasioned by leaving the foot-stalks of the fruit after this has been gathered: by carelessly applying ladders ; and especially where large boughs have been broken off, or inadvertently lopped.

This distemper may be known before the gummy secretion actually takes place, by the bark assuming a brownish cast, that gradually deepens, till the gum -at length exudes in the form of small blisters. As soon as any of these symptoms are perceived, Mr. Forsyth directs the infected part to be cut out with a sharp knife, till the clean white bark and wood appear; after which the composition and powder (see p. 238 of the present volume) should be speedily applied. Lastly, in case any gum ooze out of the tree, it must he immediately scraped off; as the disease will otherwise rapidly increase : - the best time for this operation, in the opinion of Mr. F. is during wet weather ; because the gum, being moistened, may then be easily removed without injuring the bark.