CROWN-ROT OF FRUIT TREES: HISTOLOGICAL STUDIES 487 
and 9, and the new cambium apparently started to form in the inner 
phloem just outside the dead cambium as shown by the light line near 
the wood, at the lower left. But because of marked irregularities in 
the distribution of the sheath of severest injury, the first new cambial 
initial was supplanted by one farther removed from the wood and 
overtopping the irregularities, as shown at nc. Toward the left of 
this figure the injury had been so severe as wholly to inhibit the de- 
velopment of a new cambium, although the cell proliferation had 
occurred that ordinarily precedes the production of a new cambium. 
Some of the small groups of living cells in that region had become 
light brown in color and were evidently dying. Toward the left end of 
the new cambium only scattered groups of new wood cells had de- 
veloped. The portion of old inner phloem, separated from the rest 
by the mantle of injured tissue (near the center), had grown some- 
what, but no definite cambium had been evolved. In the section 
shown in Fig. 21 similar isolated strips had developed into wood cells, 
even though the new cambium, as in Fig. 20, developed farther out 
in the phloem and produced a rather broad layer of new wood outside 
the zone of greatest injury. This type of figure seems to have been 
developed as the result of initial injuries like those shown in Figs. 5, 
7 and 9. Much dead tissue was compressed into irregular masses 
in the outer phloem and cortex. The new cambium {nc) has a brown- 
ish tinge and seems to be much collapsed. It should be noted in 
this case that the phloem left attached to the old wood was transformed 
into wood without leaving a cambium. Fig. 22 is interesting chiefly 
on account of the fact that injuries in the outer cortex resulted in the 
development of a new phellogen layer or cork cambium within {ph). 
Fig. 2, Plate XXI, shows an injury occurring mainly in the inner 
cortex, that is often similarly cut off by a phellogen developing in 
the outer phloem. Fig. 23 is somewhat comparable to the left portion 
of Fig. 20, in that no new cambium has developed, although con- 
siderable regeneration growth has occurred. The cortex is prac- 
tically uninjured and therefore appears normal from the outside, but 
both the outer and inner phloem are severely affected and the cambium 
is entirely dead, except in isolated streaks like that shown near the 
left. But even in this severely injured phloem occur groups of living 
cells, though they are more or less completely isolated by dead tissues. 
Many enormous bladdery outgrowths from the living cells are forced 
into the dead masses. In some places the living and in others the 
