484 
J. G. GROSSENBACHER 
and the outer bark. Fig. 9 shows a condition much Hke that in 
Fig. 7, excepting that larger masses of inner phloem are alive, although 
not evidently affording living links between the bark and the wood. 
In both Figs. 7 and 9 the sheath of dead tissue seems complete, thus 
isolating the bark from the wood cylinder at these places. 
The initial injuries presented in Plate XXI are not shown because 
they represent the most severe cases, but because the location of the 
injuries is typical and yet they are not severe enough to prevent 
proper handling of the sections. As noted above, material for sec- 
tioning had to be taken from portions of trees where the areas of 
individual injuries or dead patches were relatively small in order to 
prevent the shattering of the blocks before they were imbedded. 
When small blocks were cut from the very edge of one of the more 
extensive injured areas, they frequently remained intact through the 
imbedding and sectioning processes; if, however, the entire block 
was within such an area, its different portions usually fell apart, 
separating along the planes of severest injury. This falling apart 
of the blocks was less troublesome in the material collected May i 
than in that collected April 17. The blocks cut on May 29 from the 
more severely affected and larger areas were extremely fragile, while 
those from regions of less injury were more stable than specimens 
of the same degree of injury collected April 17. 
Some Changes Due to Growth and Regeneration— The figures of 
Plate XXII are made from photographs taken of sections of apple 
collected May i, 1912. These show some interesting phenomena of 
growth and regeneration, and among other things suggest how and 
why it is that so few bark injuries give rise to dead patches of bark. 
In Figs. 10, II and 12 are shown cases in which the initial injury 
involved all or nearly all of the cambium and a portion of the inner 
phloem, with dead streaks of less extent scattered in other parts of 
the phloem. In all three of these cases subsequent regeneration 
growth from the living portions of the phloem resulted in establishing 
a more or less definite living connection through the zone initially 
involved. As a result of this growth, the material in the scattered 
dead streaks in other portions of the phloem has become compressed 
into ragged plates with their edges directed toward the wood. In 
other parts of the bark dead groups of cells are similarly compressed 
by the more or less bladdery growths from the surrounding tissues. 
In Figs. 10 and 11, comparatively few of the proliferating bark-cells 
