194 SCIENCE OF GARDENING. PART II. 



Willdenow describes it as occasioning a preternatural swelling of particular parts, and in- 

 ducing putrefaction. It is said to take place chiefly in bulbous and tuberous roots, which 

 are often found much swelled after rain. It affects fruits also, which it renders watery 

 and insipid. It prevents the ripening of seeds, and occasions an immoderate production 

 of roots from the stem. 



884. Succulent plants. This disease generally appears in consequence of excessive waterings, and is gene- 

 rally incurable. The leaves drop, even though plump and green ; and the fruit rots before reaching maturity. 

 In this case the absorption seems to be too great in proportion to the transpiration ; but the soil when too 

 much manured produces similar effects. Du Hamel planted some elms in a soil that was particularly 

 well manured, and accordingly they pushed with great vigor for some time ; but at the end of five or six 

 years they all died suddenly. The bark was found to be detached from the wood, and the cavity filled up 

 with a reddish-colored water. The symptoms of this disease suggest the palliatives ; and the preventive 

 is ever the same judicious culture. 



885. Flux of juices. Some trees, but particularly the oak and birch, are liable to a 

 great loss of sap either bursting out spontaneously, owing to a superabundance of sap, or 

 issuing from accidental wounds ; sometimes it is injurious to the health of the plant, and 

 sometimes not. 



886. There is a spontaneous extravasation of the sap of the vine, known by the name of the tears of the 

 vine, which is not always injurious. As it often happens that the root imbibes sap, which the leaves are not 

 yet prepared to throw off, because not yet sufficiently expanded, owing to an inclement season, the sap which 

 is first carried up, being propelled by that which follows, ultimately forces its way through all obstructions, 

 and exudes from the bud. But this is observed only in cold climates ; for in hot climates where the 

 developement of the leaves is not obstructed by cold, they are ready to elaborate the sap as soon as it 

 reaches them. There is also a spontaneous extravasation of proper juice in some trees, which does not 

 seem in general to be injurious to the individual. Thus the gum which exudes from cherry, plum, peach, 

 and almond trees, is seldom detrimental to their health, except when it insinuates itself into the other 

 vessels of the plant and occasions obstructions. 



887. But the exudation of gum is sometimes a disease, and one for which there is seldom any remedy. It 

 is generally the consequence of an unsuitable soil, situation, or climate. Cold raw summers will produce it 

 in the peach, apricot, and more under-sorts of plum and cherry ; or grafting these fruits on diseased stocks. 

 Cutting out the part and applying a covering of loam or tar and charcoal to exclude the air are palliatives ; 

 but the only effectual method, where it can be practised, is to take up the tree and place it in a suitable soil 

 and situation. 



888. The extravasation and corruption of the ascending or descending juices, has been known to occasion 

 a fissure of the solid parts. Sometimes the fissure is occasioned by means of frost, forming what is called a 

 double alburnum ; that is, first a layer that has been injured by the frost, and then a layer that passes into 

 wood. Sometimes a layer is partially affected, and that is generally owing to a sudden and partial thaw 

 on the south side of the trunk, which may be followed again by a sudden frost. In this case the alburnum 

 is split into clefts or chinks, by means of the expansion of the frozen sap. 



889. Chilblains. But clefts thus occasioned often degenerate into chilblains that discharge a blackish and 

 acrid fluid to the great detriment of the plant, particularly if the sores are so situated that rain or snow will 

 readily lodge in them, and become putrid. The same injury may be occasioned by the bite or puncture of 

 insects while the shoot is yet tender ; and as no vegetable ulcer heals up of its own accord, the sooner a 

 cure is attempted the better, as it will, if left to itself, ultimately corrode and destroy the whole plant, bark, 

 wood, and pith. The only palliative is the excision of the part affected, and the application of a coat of 

 grafting wax. ( WiUdenow, p. 354.) 



890. Gangrene. Of this disorder there are two varieties, the dry and the wet. The 

 former is occasioned by means of excessive heat or excessive cold. If by means of cold, 

 it attacks the leaves of young shoots and causes them to shrink up, converting them from 

 green to black ; as also the inner bark, which it blackens in the same manner, so that it 

 is impossible to save the plant except by cutting it to the ground. If by means of heat, 

 the effects are nearly similar, as may oftentimes be seen in gardens, or even in forests, 

 where the foresters are allowed to clear away the moss and withered leaves from the roots. 

 Sometimes the disease is occasioned by the too rapid growth of a particular branch, de- 

 priving the one that is next it of its due nourishment, and hence inducing its decay. 

 Sometimes it is occasioned by means of parasitical plants, as in the case of the bulbs of 

 the saffron, which a species of lycoperdon often attaches itself to and totally corrupts. 



891. Dry gangrene. The harmattan winds of the coast of Africa kill many plants, by means of in- 

 ducing a sort of gangrene that withers and blackens the leaves, and finally destroys the whole plant. The 

 nopal of Mexico is also subject to a sort of gangrene that begins with a black spot, and extends till the 

 whole leaf or branch rots off, or the plant dies. But plants are sometimes affected with a gangrene by which 

 a part becomes first soft and moist, and then dissolves into foul ichor. This is confined chiefly to the 

 leaves, flowers, and fruit. Sometimes it attacks the roots also, but rarely the stem. It seems to be owing, 

 in many cases, to too wet or too rich a soil ; but it may originate in contusion, and may be caught by in- 

 fection. But the nopal is subject also to a disease called by Thiery la dissolution, considered by Sir J. E. 

 Smith as distinct from gangrene, and which appears to be Wittdenow's dry gangrene. A joint of the 

 nopal, or a whole branch, and sometimes an entire plant, changes in the space of a single hour, from a 

 state of apparent health to a state of putrefaction or dissolution. Now its surface is verdant and shining, 

 and in an instant it changes to a yellow, and its brilliancy is gone. If the substance is cut into, the parts are 

 found to have lost all cohesion, and are quite rotten ; the attempt at a cure is by speedy amputation below 

 the diseased part Sometimes the vital principle collecting and exerting all its energies, makes a stand 

 as it were against the encroaching disease, and throws off the infected part. (Smith's Introduction, p. 340.) 



892. Etiolation. Plants are sometimes affected by a disease which entirely destroys 

 their verdure, and renders them pale and sickly. This is called etiolation, and may arise 

 merely from want of the agency of light, by which the extrication of oxygen is effected, 

 and the leaf rendered green. And hence it is that plants placed in dark rooms, or be- 

 tween great masses of stone, or in the clefts of rocks, or under the shade of other trees, 

 look always peculiarly pale. But if they are removed from such situations, and exposed 



