OF FRUIT TREES. 33 



the southwest side of the trunk or body of the trees. 

 There it generally commences, and continues to in- 

 crease annually, until the infection is communicated 

 to the limbs. If I might be permitted to hazard an 

 opinion, 1 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 angles. 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 gen- 

 erally incline to the northeast, which exposes their 

 trunk 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 deciduous trees) is accelerat- 

 ed by the hot rays of the sun at southwest. It is re- 

 tarded and stagnated in the cool of the nights, where- 

 by the irritability of the vegetable vessels is decreas- 

 ed for want of a sufficient stimulus of heat; and by 

 this alternate thawing and freezing of the sap-juice, 

 and particularly 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 

 frequently happens, that scions for grafting are taken 

 from infected trees ; and the young trees produced in 

 this way are, as might be expected, peculiarly obnox- 

 ious to the disease. From whatever cause the canker 

 may arise, Mr. Forsyth directs all the diseased parts 

 to be cut out with a sharp instrument ; and if the 

 inner white bark be affected, this also must be cut 

 away, until no appearance of infection 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 compo- 

 sition, page 73.) Mr. Cooper, of New Jersey, has 

 found the best remedy for canker to be a composition 



