126 ACCIDENTS AND DISEASES OF PLANTS CONSIDERED. 



prevented this disease from attacking his late crops of Peas, The rust 

 in corn crops is produced by a fungus in the same manner as the mildew ; 

 but as it chiefly concerns the agriculturist, we refer the reader to Professor 

 Henslow's Report of the Diseases of Wheat, Jour. Ag. Soc. Eng., vol. ii. p. 1. 



380. Honey dew is a sweet and clammy exudation from the surface of the 

 leaves of plants during hot weather, and it is supposed to be occasioned by 

 the thickening of the circulating fluids in the leaf, which being unable to 

 flow back into the bark with their accustomed rapidity, the sugary parts find 

 their way to the surface. The disease is common in the Oak, Beech, Thorn, 

 and in many other plants. Hitherto no remedy has been applied to it in 

 general cases, as though it weakens plants it seldom kills them. When, 

 however, it appears on plants in a state of high cultivation, for instance, in a 

 peach-house, or on a peach- wall, no time ought to be lost in applying the 

 syringe or garden-engine, and even rubbing it off^ the leaves if necessary, 

 otherwise the shoots or branches affected will be apt to be destroyed. Some 

 persons suppose the honey dew to be occasioned by the aphides, as the 

 exuviae of those insects are often found on leaves aff^ected with this disease. 



881. Blight is a term which is very generally applied to plants when under 

 the influence of disease, or when attacked by minute fungi or insects. In 

 some cases the continued action of dried air, and cold frosty winds, preventing 

 the flow of the sap, may bring on a disease which might be called blight, 

 exclusive of either the action of insects or of fungi ; but by far the greater 

 number of instances of what is called blight are produced by these two causes. 

 In general the fungi may be destroyed by the application of powdered sulphur, 

 and the insects by some of the dififerent means that have been already pointed 

 out (352 to 861). 



382. Flux of Juices. — Under this term are comprehended the bleeding, or 

 flow of the juices of the vine and other plants, when accidentally wounded, 

 or pruned too early in autumn, or too late in spring ; and the discharge of the 

 descending sap, or the cambium, in a putrid state between the bark and the 

 wood, which frequently happens in elm-trees, and is incurable. The flux of 

 the rising juices seldom does much injury, and may generally be prevented 

 by pruning before the sap is in motion. 



383. The accidents to which plants are liable are chiefly confined to the 

 plants being broken or bruised, and the general remedy is amputation of the 

 parts. When the section of amputation is large, it is best to cover the 

 wound w^ith some adhesive composition, which will exclude the weather, 

 and not impede the gi'owth of the bark over the wound ; but this subject 

 will be noticed more in detail when we come to treat of pruning. 



884. A number of other plant diseases have been described and named by 

 writers on Botany, but they are of very little interest to the practical gar- 

 dener, because they rarely occur when plants are properly treated, or occur 

 only in old age, or in a state of natural decay ; or because, when they do occur, 

 they seldom admit of any remedy. Those diseases to which some plants 

 are more liable than others, will be mentioned when these plants are treated 

 of ; for example, the rot in the Hyacinth, the dropsy in succulents, the blis- 

 tering of the leaves in Peach-trees, &c. 



