290 Eeport of the Botanical Department of the 



28 and short sections were taken from the typical regions and pre- 

 served in alcohol until they could be photographed. Figures 1 to 7 

 on Plates XXVIII and XXIX show sections of some of these injured 

 regions. 



Figure 1 is a section about 15 cm. above ground and 2 cm. below 

 the lower end of the cleft in the bark. Its greatest diameter is 7.6 cm. 

 In a section taken about 3 cm. nearer the ground there was but a 

 trace of loosening of the bark, while in one taken 2.5 cm. above 1 

 the loosened area is wider and there has been an appreciable growth 

 of callus along one edge. In the section shown in figure 1 the bark 

 was not entirely loose; the injured region in the inner phloem seemed 

 to offer slight resistance to the removal of the bark. The isolated 

 bark was almost of normal color in figures 1 and 2 except at the 

 margins of the cleft of 2. In figure 3 which was taken 2 cm. above 2, 

 the loosened bark was slightly discolored and seemed to be nearly 

 dead. The cleft in the wood shown in figure 3 to begin near the 

 cleft in the bark and extending toward the pith through two annual 

 growths may also be seen in figure 2. In figure 4 the bark above 

 had died while that below the cleft was still partially alive. Figure 5 

 is taken above the middle of the cleft and shows the typical appear- 

 ance of the region of maximum injury of both bark and wood. The 

 loose bark is entirely dead and stands out away from the wood owing 

 to the callus growths around the periphery of the wound and to the 

 entire lack of adherence between the bark and wood. At the lower 

 left of the figure some regeneration had occurred on the surface of 

 the exposed wood. 



In the region of the trunk about midway between the ends of the 

 cleft in the bark the wood had been split through the pith to the 

 inner side of the bark on the opposite side, but leaving the bark unin- 

 jured. A rather conspicuous ridge of new wood had developed over 

 the end of the wood cleft; it was about as thick as the callus growth 

 at the lower left margin of the loose bark shown in figure 5. 



Figure 6 is taken about a centimeter above the upper end of the 

 bark cleft and 15 cm. above figure 5. Here as in figure 1 no cleft 

 resulted in the wood and the partially loosened bark was still alive. 

 Figure 7 is of a section 3.2 cm. above that shown in figure 6 and about 

 5 cm. below the main crotches. The strip of injured bark is shghtly 

 wider at this point Imt is of normal color and seems to have grown 

 in thickness by the development of new wood on the inner side of the 

 bark against last year's growth. 



As these figures plainly show, the increase in the diameter of this 

 tree trunk in 1911 was nearly as much as that of any two previous 

 seasons and therefore the bark had to increase enormously in area 

 to adjust itself to the unusual increase in wood growth. The field 

 observations on fruit trees also seem to show that bark on tree-trunks 

 which increase unusually in diameter during one summer is most 



