120 



Principles of Plant Culture. 



a heat that is fatal to the foliage beneath them. This 

 may explain the brown spots so often observed upon the 



leaves of indoor plants that 

 have been sprinkled in bright 

 sunlight. Sometimes, but rare- 

 ly, this trouble occurs in the 

 open air. 



185. Sun-Scald is the term 

 applied to an afPection of the 

 trunk and larger branches of 

 certain not quite hardy trees, 

 usually upon the south or 

 southwest side, in which the 

 bark and cambium layer (68) 

 are more or less injured (Fig. 

 58). In severe cases, the cam- 

 bium is totally destroyed, and 

 the loosened bark splits longi- 

 tudinally or becomes detached. 

 The effect is apparently the 

 same as when a tree is exposed 

 to the heat of a fire. Sun-scald 

 is most common in young trees, 

 especially in those recently 

 transplanted or overpruned. 

 It appears to be due, in some 

 cases, to the superheating of 

 the cambium in summer — in 

 others to a return of severe freezing weather after a 

 period sufficiently warm to excite the cambium cells to 

 activity. A preventive is to shade the trunk and larger 



Fig. 58. Showing etEects of 

 sun-scald on trunk and 

 branches of silver maple tree, 

 Acer dasycarpum. 



