CH. VIII,] THE DISEASES OF PLANTS. 308 



injured part, the discharge is often protracted. This 

 is especially the case, if the wound he made in 

 the spring, hefore the leaves are developed, as in 

 performing the vrinter pruning of the vine later 

 than is proper. In such case the vine is always 

 weakened, and in some instances it has been destroyed. 

 The quantity of sap which may be made to flow from 

 some trees is astonishing, especially in tropical 

 climates. Thus from a cocoa-nut palm, fi'om three 

 to five pints of sap will flow dming eveiy day for 

 four or five successive weeks. 



The best mode of checking such exudations, is by 

 placing a piece of sponge dipped in a solution of 

 sulphate of iron, upon the discharging place, covering 

 the sponge with a piece of sheet lead, and binding 

 it on firmly. The sulphate acts as a styptic, pro- 

 moting the contraction of the mouths of the vessels ; 

 the sponge encourages cicatrization, and the lead 

 excludes moisture. 



5. Heat, attended by dryness of the soil, as during 

 the drought of summer, is very liable to produce an 

 unnatural exudation. This is especially noticeable 

 upon the leaves of some plants, and is popularly 

 known as honey-dew. It is somewhat analogous to 

 that out-burst of blood which, in such seasons, is 

 apt to occur to man, and arises from the increased 

 action of the secretory and circulatory systems to 

 which it affords relief. There is this great and 



