Plants as Affected by Heat. 



117 



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 rarely, this 

 trouble occurs in the open air. 

 186. Sun-scald is the term ap- 

 plied to an affection of the 

 trunk and larger branches of 

 certain not quite hardy trees, 

 usually upon the south or south- 

 west side, in which the bark 

 and cambium layer (69) are 

 more or less injured (Fig. 58). 

 In severe cases, the cambium 

 is totally destroyed, and the 

 loosened bark splits longitudin- 

 ally or becomes detached. The 

 eifect is apparently the same as 

 when a tree is exposed to the 

 heat of a fire. Sun-scald is 

 most common in young trees 

 and 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 suf- 

 ficiently warm to excite the 



FIG. 58. Showing effects of sun- p^hinni pplU to flrtivitv A 

 scald on trunk and branches of C tlVlty. ^ 



silver maple tree, Acer dasycar- preventive is to shade the 



trunk and larger branches by 



inclosing them with straw or similar material, or with a- 

 lath screen (Fig. 59). 



