486 
J. G. GROSSENBACHER 
a nearly complete sheath, thus isolating the cortex considerably 
from the phloem. A scattering of living cells occurs, however, in 
this outer-phloem zone to afford water and nutrient transfer between 
the outer and inner barks sufficient to permit the outer bark to endure 
at least for a time. 
The figures of Plate XXII likewise give only a few of the great 
variety of the injuries that were mild enough to permit rnore or less 
regenerative growth during the spring, although some of the figures 
plainly indicate that only a most favorable summer would enable 
the affected bark to survive. 
Some Results Found at the End of May. — Plates XXIII and XXIV 
give an idea of the great variety of results following some of the initial 
injuries shown on Plate XXI. The low-power views collected on 
Plate XXIII make it evident that regeneration and growth of the 
living cells are not all that is required to sustain the affected bark and 
to keep it from dying in early summer. Figs. i8 to 22 inclusive show 
some of the milder forms, while Figs. 23 to 26 indicate various stages 
and degrees of injury resulting in the death of patches of bark. 
Fig. 18 shows an advanced stage of an initial injury of the type 
shown in Figs. 7 and 9, and, in later condition, in Figs. 10 and 11. 
The new cambium sheath arose much after the manner shown in 
Fig. 17. The compressed fragments of dead tissues, present at the 
time spring growth started, are noticeable in the new wood {nw) 
as well as in the old phloem {op). The initial injury was so severe 
that the old wood and bark-rays were not continued by the new 
growth; new rays are just becoming differentiated on both sides of 
the new cambium {nc). In this case the outer bark seems to have 
established sufficient living connection with the regenerating inner 
bark to continue its normal functioning, but the connection between 
the old {ow) and the new wood {nw) seems to be insufficient in places, 
for the new cambium {no) has also developed in the inner phloem. 
In this case the initial injuries in the outer phloem and cambium were 
so extensive as greatly to delay the development of the new cambium 
{nc), as seen near the middle of the figure. No definite new wood 
cells have yet been formed at this point, although on both the right 
and left sides a considerable layer of new wood has resulted and the 
new cambium appears practically normal. Fig. 20 shows some inter- 
esting irregularities in the distribution and configuration of the initial 
injuries. They had evidently been of the type shown in Figs, i, 5 
