510 
J. G. GROSSENBACHER 
Fig. 20. Mantle of greatest injury with irregular course. At the right the 
new cambium (nc) has begun the development of a new layer of wood (nw), while 
at the left no substitute cambium is yet visible. 
Fig. 21. More irregularity in the course of the mantle of greatest initial injury. 
Living phloem is left attached to the old wood {ow) and converted into wood without 
leaving an accive cambium. New cambium (nc) has developed outside the zone 
of injury that produced the layer of wood. The cambium has become abnormal, 
yellowish in color, and is partly disorganized. Discolored streaks extend from it 
into both new wood (nw) and new phloem (np). 
Fig. 22. Much like Fig. i8, showing in addition a new phellogen (ph) cutting 
off the outer part of the cortex. 
Fig. 23. Exaggerated form shown near the left end of Fig. 20. No new 
cambium is in evidence, and dead matter predominates, although from the outside 
the bark appeared normal. 
Fig. 24. A case in which the most severely injured portions of the bark died 
and a callus (cal) developed along its margin. New wood (nw) at the lower right 
arose without leaving cambium. 
Fig. 25. Severe initial injury confined to a small space. Although much 
isolated from the old wood, the callus is normal, having an active cambium. As in 
Fig. 24, fungus mycelium is present in the dead bark and in the dead mantle between 
the callus and the dead wood. 
Fig. 26. Bark half-way around stem is dead and sunken, much like the patch 
shown in Fig. 41. In cross-section this looked like a miniature of the specimen 
shown in Fig. 50. Mycelium and pycnidia of a bark fungus were present. 
Plate XXIV 
Higher power views of some injured tissues in the stage shown on Plate XXIII. 
Fig. 27. View of a region like that in oc of Fig. 18. Living connections 
through the dead region are evidently few and imperfect. 
Fig. 28. Like Fig. 27. Former phloem rays have become discontinued and 
have undergone division and become converted into callus tissue. 
Fig. 29. Copied from Sorauer's paper on " Frostschorf " of apple and pear in 
Zeitschrift fiir Pflanzenkrankheiten, i: 137-45. 1891. Cortical injury that usually 
precedes premature bark-roughening. 
Fig. 30. Magnified view of the type shown in the center and right of Fig. 19; 
substitute cambium (nc) developed in a meandering course. Much-injured bark 
practically isolated from the old wood {ow). 
Fig. 31. Detail of a case something like that shown in Fig. 22, excepting that 
practically no new phloem has yet developed; new cambium {nc) is considerably 
disorganized and discolored. Old phloem {op) is permeated by initially killed 
tissue, in direct contact with disintegrating new cambium. 
Fig. 32. Much like Fig. 30; only a faint indication of substitute cambium {nc) 
is in evidence. Injury in old phloem is more severe than in Fig. 30; cells in regenera- 
tion-growth are less affected by pressure than those in Fig. 30. 
Fig. 33. Higher power view of case like that in left-hand portion of Fig. 20, 
with uncommonly thick mantle of dead tissue. Living portions of former bark 
rays are converted into ordinary parenchyma. 
