SECT.%1. DISEASES. 



ous. 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 exude* 

 from the bud. But this is observed only in cold 

 climates ; for in hot climates, where the develope- 

 ment of the leaves is not obstructed by cold, tbef 

 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 Chery, 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. 



But when the sap ascends more copiously than it In what 

 can be carried off, it sometimes occasions a fissure of judieal. 

 the solid parts, inducing disease or deformity by en- 

 couraging the extravasation and corruption of the 

 ascending or descending juices. Sometimes the 

 fisssure 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 par- 

 tially 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, 



