OF FRUIT TREES. 79 



f the trees. There it generally commences, and 

 continues to increase annually, until the infection is 

 communicated to the limbs. If I might be per- 

 mitted to hazard an opinion, I would account for it 

 as follows : That it is caused by the hot rays of 

 the meridian sun, which in that direction is most 

 powerful, and strikes the tree nearly at right an- 

 gles. The south side of trees grows faster, for 

 there the vegetation is more rapid, than the north: 

 this may be seen by the concentrick rings of a tree 

 when cut or sawed into logs. Fruit trees gene- 

 rally incline to the northeast, which exposes their 

 trunks to the influence of that luminary in the 

 spring, when the sap-juice is subject to alternate 

 freezing and thawing. The motion of the sap 

 (which ascends in the vernal months in all deci- 

 duous trees) is accelerated by the hot rays of the 

 sun at southwest. It is retarded and stagnated in 

 the cool of the nights, whereby the irritability of 

 the vegetable vessels is decreased for want of a 

 sufficient stimulus of heat ; and by this alternate 

 thawing and freezing of the sap-juice, and particu- 

 larly on the southwest side of the tree, where the 

 sun's rays are most powerful, the vegetation is at 

 last destroyed, and mortification ensues." It fre- 

 quently happens, that scions for grafting are taken 

 from infected trees ; and the young trees produced 

 in this way are, as might be expected, peculiarly 

 obnoxious to the disease. From whatever cause 

 the canker may arise, Mr. Forsyth directs all the 

 diseased parts to be cut out with a sharp instru- 

 ment ; and if the inner white bark be affected, this 

 also must be cut away, until no appearance of in- 

 fection remains. The composition must then be 

 applied. This method Mr. Yates has found by 

 experience to prove effectual. (See directions for 

 making and laying on the composition, page 69.) 

 Mr. Cooper, of New Jersey, has found the best 



