CROWN-ROT OF FRUIT TREES: HISTOLOGICAL STUDIES 489 
some of the new wood (nw) cells are becoming discolored. This 
intermingling of living and dead groups of cells is most common in the 
phloem. The position of the new cambium (nc) is occupied chiefly 
by structureless masses having a yellowish brown color. The cortex 
and outer phloem had only scattered groups of dead cells. No 
fungous hyphae could be detected in this specimen. Fig. 32 shows 
tissues which had sustained more severe initial injuries but which, 
because of the small area of the most severely affected part, endured 
quite well, while in the case of milder injury but of larger area shown 
in Fig. 31 the tissues seemed to be dying. In the tissues shown in 
Fig. 32, the outer phloem also is largely killed but the cortex is in fair 
condition. A new cambium (nc) is forming near the old wood. At 
this place no living connection appears between the bark and the 
wood, but because of the smallness of the region so severely affected, 
the necessary water and nutrients seem to reach it from the sides 
of the injured patch where such connections do occur. Fig. 33 shows 
a case in which much of the inner phloem had been killed and in 
which very active filling-growth is occurring. A faint indication 
of the formation of a new cambium can be seen here and there; a 
spot of this kind appears near the center of the figure. The photo- 
graph from which Fig. 34 was made shows a very large group of dead 
phloem tissue which has been only partly permeated by proliferating 
cells arising from living adjoining cells. In some cases the initially 
killed strips of tissue form an anastomosing network lengthwise through 
the bark; in extreme instances only anastomosing streaks of inner 
bark may be alive while the greater mass of the bark is dead. A 
cross section of such a living streak in great masses of dead tissue 
may be seen in Fig. 35. In this instance large groups of dead cells 
also occurred in the inner cortex, although when the specimen was 
cut (May 29) its external appearance was practically normal. 
From another type of initial injury enlargements as well as wood- 
exposures occur on trunks of trees. Such cases of excessive enlarge- 
ments on trunks may sometimes develop from initial injuries of the 
type shown in Fig. 3, Plate XXI, in which a definite separation or a 
concentric cleft has resulted, and where at the same time the repair 
growth and connection with the wood are such as to prevent the dying 
of the loosened outer bark. When radial clefts run through such 
areas and the bark is otherwise sufficiently intact to withstand the 
drying action of air, the repair growths may turn the edges of the 
