48o 
J. G. GROSSENBACHER 
beginnings depends mainly upon the relative extent and number of 
the injured or dead patches, upon the weather of the ensuing growing 
season, and possibly upon the relative abundance of wound fungi. 
In many of the milder cases, the injured and collapsed tissues are 
merely more or less compressed by the subsequent growth of the 
surrounding live parenchyma cells, and in late summer only the 
presence of irregular formless dead masses among the living tissues 
of the bark tells the story of the former trouble. In the more severe 
cases, however, in which in addition to the medullary rays of the 
phloem, the inner portions of the cortex and perhaps most of the 
cork cambium have been much injured, the results are likely to be 
more serious. In these cases, as in the milder ones, the resumption 
of growth by the surrounding live parenchyma results in the com- 
pression of the dead and dying tissues; but since the dead patches are 
numerous, relatively large, and close together, the intervening live 
parenchyma and ray-cells are insufficiently supplied with water and 
nutrients and therefore cannot survive the drying weather of late 
spring and early summer. During the latter part of this process a 
new cork cambium is developed inside the dying cortical parenchyma, 
resulting afterward in a rough, scaly bark. In cases where the 
initial injury involves very large patches of outer phloem but leavet 
the inner phloem and practically all the cambium intact, the resuls 
is approximately the same, excepting that occasionally small patches 
of bark die to the wood on account of the occurrence of coincident 
injured patches in the cambium and inner phloem. It often happens 
in instances of this kind that the cortex is affected but slightly and 
that it retains its normal appearance until the internal trouble has 
become far advanced; then it usually dies rather quickly and dries 
out. However, none of the types of injury so far described usually 
result in very serious trouble because at most only small areas of 
bark are killed to the wood. 
When most of the cambium and much of the phloem are initially 
affected, the injurious results are usually much more evident; but 
even in such cases the bark may survive if the weather is favorable 
and if the area affected is not extensive as compared with the total 
area of the bark of that portion of the stem. In case the injured 
patches in the cambium and inner phloem are relatively large or fairly 
close together, or if they form nearly continuous sheaths of affected 
tissues, the regenerations from the living portions of the bark are 
