543. What is called suffocation is very commonly induc ed by the stems and branches being overgrown with lichens and mosses ; an evil to which the trees in old orchards, where perhaps the bottom is naturally moist, and has not been drained, are peculiarly liable. The remedy is simple, consisting in rubbing off the parasitical plants, an opera tion which is much more easily and effectually performed in wet than in dry weather. A round-mouthed iron scraper is sometimes used for this purpose ; but one of hard wood answers perfectly well. The trunk and larger branches are afterwards hard swept with a birchen rubber, and it is found very useful, even after both these operations, to wash the branches with old soap-suds or any penetrat ing liquid, or to apply a coating, of the consistence of paint, of a mixture of equal parts of quicklime, cow dung, and clay.
544. Sometimes blotches or dark spots appear, termi nating in ulcers. If these occur on old branches, the best remedy is to cut off the diseased parts, if practicable, and to apply a plaster. This may be composed of horse-drop pings and clay wrought together, these ingredients being found to answer every useful purpose. Many however pre fer a mixture of cow dung and old time ; and where the wounds are small, this is more easily applied. This last, indeed, is very nearly Forsyth's " composition," the speci fication of which the reader may like to see. It is as Take one bushel of fresh cow-dung, half a bushel of litre rubbish of old buildings, half a bushel of wood a sixteenth part of a bushel of pit or river sand; the three last articles to be sifted fine before they be mix ed ; then work them well together with the spade, and af terwards with a wooden beater, until the stuff is very smooth, like fine plaster used for the ceilings of rooms. Chamber iye and soapsuds are to be added, till it be reduced to the consistence of a pretty thick paint, which may be applied to the trees with a painter's brush. The application of such plagters or paints, it may here be remarked, is proper wherever any accident has occurred to fruit trees,or where large branches are lopped off.
In some cases, especially in peach-trees, blotches appear on the young shoots, which must of course be entirely re moved. Mr. Kinment, gardener at Murie in Scotland, has assigned some reasons for believing that such blotches on the young wood of the peach-tree, are induced by the gross feeding of the tree; in other words, he observed, that blotches always occurred on trees where the borders were manured with simple dungs, but that where fresh soil or well prepared compost only was added to the bor der, the trees continued in a healthy state.
545. When a tree becomes hide bound, or when the stem swells too fast for the bark, the usual remedy is, with a knife, to score or divide the outer bark longitudinally in various places.
546. In cases where the outer bark has become rough and full of chinks, so that small insects deposit their eggs and produce their larva below this bark, it is a good prac tice entirely to remove it. This sort of decortication is by no means a novelty in gardening ; it is recommended by several of the authors mentioned in the it to this article. Thus, Le Gendre, (§ 10 ) writing; :.gout 1650, says, Those trees which have their bark base, ou must with a bill take away the old bark to the quick ; for the trees being thus cleared and discharged, do shoot forth with new strength, bearing fairer and I.tt•r now ished fruit." (Translation, p. 136 ) And Hitt (§ 14) who wrote in 1754, recommends for trees that have been neglected or ill dressed, tt taking- off the old rind, and cleansing can leered parts, thus destro) ing many insects. as also their eggs, concealed in these places." (Treatise on Fruit Trees, 3d edit. p. 271.) Of late years Alt Knia;ht prac tised decortication on 50111e 01(1 fruit trees, p red streak apples, and found the new growth thus produced quite surprising, so that the growth of some trees de prived of their external bark in 1801, exceeded in the summer of 1802, the increase of the five preceding years taken together. (7'rratise on Apple and l'ear, 4th edition, p. 86 ) 547. More recently, a zealous horticulturist at Edin burgh, Mr P. Lyon, surgeon, has called the attention of the public to the advantages of deco! tmation. At first Mr Lyon recommended the removal of the hark only in cases where it was cracked and rugged, and chiefly with the view of destroying the ova of insects ; but of late he has inculcated the stripping off the outer bark even of young trees, and of the new shoots of full grown trees, even where the bark is sound and healthy. The beneficial ef fects of the former practice we have repeatedly witnessed; old trees which usually bore very little fruit, and produced little new wood, becoming, after the removal of the outer bark, fruitful, and rather exuberant in the production of shoots : the fruit, however, though plentiful, has in gene ral been of smaller size than usual. The depriving young trees and new shoots of their bark is quite a different thing. We know that it is the earnest endeavour of many excellent practical gardeners to keep the bark on, provid ed they can preserve it in a clean and healthy state. We shall only, therefore, for an explanation of this part of Mr Lyon's doctrines, refer to his book, entitled " A Treatise on the Physiology and Pathology of Fruit-trees," 8vo. Edin. 1816,—warning the reader that he must make allow ance for no small proportion of extraneous matter.