166 Report oF THE BoOTANIST OF THE 
If the injury is severe and occurs before the leaves are fully 
grown,°® the injured leaves fall and new ones appear, but if the 
injury occurs after the leaves are full grown they remain attached 
to the twigs until late in autumn. In the latter case some of the 
leaves will be found wholly dead, but the majority of them will 
show a dead, brown portion and a living, green portion. As a 
rule, especially on the sugar maple, the dead portion is located 
around the margin of the leaf (see Plate IX, fig. A), but it may 
occur in the form of circular or irregular blotches; or the margin 
of the leaf may be occupied by living, green tissue surrounding a 
dead area at the center (see Plate IX, fig. B). In all cases the 
living tissue is separated from the dead by a sharply defined line. 
The color of the dead tissue is either light brown or reddish brown. 
The injured leaves for the most part remain expanded. 
As with the beet, cherry and cauliflower, this injury to maple 
foliage occurs in a comparatively short space of time. It happens 
whenever the quantity of water transpired by the leaves is greater 
than that which the roots are able to supply; and this condition of 
things may be brought about in several ways. Some of the 
factors which enter into the problem are: Area of leaf surface 
exposed, quantity of water in the soil, activity of the roots, and 
location of the tree as regards exposure to wind. Having in mind 
these several factors, it is easy to understand how one tree may 
be seriously injured while another tree standing close beside it 
may not be affected at all. This is of common occurrence. 
In nurseries the disease often escapes notice until the dead 
leaves have become overgrown with various saprophytic fungi 
which are likely to be mistaken for the cause of the trouble. - 
Trees recently transplanted may die-from the effects of leaf 
scorch, but established trees rarely show any permanent injury. 
8 Observations upon the scorehing of immature maple foliage have been re- 
ported by Stone, G. E., and Smith, R. E. Wilt of Maple Leaves, Ninth Ann. 
Rept. Hatch Exp. Sta., of Mass. Agr. Coll.: 81-82; also by Stewart, F. C. 
Norway Maples Injured by Dry Winds. Fifteenth Ann. Rept. of this Station: 
453-454. 
