46 NEW YORK STATE MUSEUM 



underlying living and necessary vital tissues. This latter was in- 

 dicated first by brown spots in the inner bark, these discolored 

 parts becoming deeper, extending in area and eventually including 

 all the inner bark and most of the outer active layers of wood. 

 There was then a gradual progressive dying from the points where 

 the tissues had been killed. This latter means the death of limbs 

 and branches above the injury and may involve considerable below, 

 unless the tree possesses sufficient vitality or so little oil has been 

 applied that the maple is able to prevent further invasion of its living 

 tissues. The more vigorous vital portions below may produce 

 suckers, though in some instances even these may succumb later. 

 The injury does not necessarily involve all the lower branches; it 

 may be limited to a few on all sides of the tree or to several on one 

 side, the determining factor, in our estimation, being the amount of 

 oil applied locally. There may be a late dying of individual branches 

 and there are good reasons for believing that not all the injury may 

 become apparent at the end of the first or even the second season 

 following the application. 



Other changes may occur in conjunction with the death of the 

 limbs. The bark on the trunk, especially if this be smooth and 

 comparatively thin, may be so seriously affected that large areas die. 

 July i6th, the bark on the trunk of one tree and at the base of the 

 affected branches was badly cracked, these cracks being 12 to 15 

 inches long. September 24th there was a white fungus showing at 

 the base of the lower limbs and also on the trunk to a distance of 

 about 4 feet from the ground. An examination at this later date 

 showed that considerable areas of the bark on the trunk were dead 

 and loose, though the cracking was in an incipient stage. Some of 

 the bark on the base of the larger affected limbs was loose and 

 nearly ready to drop. The trunk of the tree at this time had been 

 entered by a number of Ambrosia beetles, the insects unconsciously 

 giving testimony to the dying or dead condition of the underlying 

 tissues. 



SIGNS OF OIL INJURY 



Severe injury following application of oil preparations appears 

 earher in the season than that due to drought and, as pointed out 

 above, is frequently limited to the lower branches, a condition al- 

 most never seen in the case of trees suffering from fungous affec- 

 tion, insect attack, drought or other adverse conditions. The injury 

 may be comparatively slight and followed by enlarged lenticels, the 

 discoloration, death and cracking of the outer layers of the bark 



