78 SYLVA AMERICANA. 



corruption of the ascending or descending juices. 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 the 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. But a cleft thus occasioned often degenerates into a 

 childblain that discharges a blackish and acrid fluid to the great 

 detriment of the plant, particularly if the sore is so situated .that 

 rain or snow will readily lodge in it, 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 remedy is applied to it the 

 better, as it will, if left to itself, ultimately corrode and destroy 

 the whole plant, bark, wood and pith. The only remedy is the 

 excision of the part affected, and the application of a coat of 

 grafting wax. 



7. Gangrene. Of this disorder there are two varieties, the 

 dry and the wet. The former is occasioned by the means of 

 excessive heat or 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 often times be seen in gardens, or even in 

 forests, where the foresters clear away the moss and withered 

 leaves from the roots. Sometimes the disease is occasioned by 

 the too rapid growth of a particular branch, depriving the one 

 that is next to 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, to which a 

 species of Lycoperdon often attaches itself and totally corrupts. 

 The harmattan winds of the coast of Africa kill many plants, by 

 means of inducing a sort of gangrene that withers and blackens 

 the leaves, and finally destroys the whole plant. The nopal of 



