te inner bark is quite healthy, generally for a thickness of 5-7 mm.
That the mycelium in the small lesions was unquestionably the _Endothia_
mycelium, was shown by the appearance of the mycelium, and the presence
of the _Endothia_ pustules in many of the spots. That these were not
late infections, but only slowly growing small lesions, was shown by
inoculations in such bark, which revealed scarcely any growth after two
months.

[Illustration: FIG. 1

One of the most resistant trees, the smaller tree near the center of the
photograph, near the Harlem River, Boro of Manhattan, New York City.]

[Illustration: FIG. 2

A very strikingly resistant tree at Valley Stream, Long Island, showing
peculiar inner bark. The outer bark is sloughing off.]

[Illustration: FIG. 3

One of the "strip" trees in the forest in the Boro of Manhattan, New
York City.]

[Illustration: FIG. 4

Showing the character of the inner bark of the Valley Stream tree (Fig.
2). At one place, near the center of the photograph, the bark has been
shaved showing the small lesions caused by the fungus.]

3. THE WHITE SECRETION.--The most striking peculiarity of the
callus tissue, is its abundant content of a thickish, milky, white
substance. This came to light immediately when I cut into the callus,
and it showed up very clearly when I shaved off the outer layers of dead
cork tissue. The white material is not evenly distributed through the
irregular grain of the wound tissue, but is particularly abundant in
small spots or pockets which are especially conspicuous in the callused
margin of the lesion. Soon after exposure to the air the cut bark, and
particularly the white substance, redden rapidly, indicating oxidation.
This peculiarity is of course true of all chestnut bark, yet here the
reddening seems to be deeper and more rapid than the normal. No chemical
analysis has yet been made of this substance, but there is
sufficient other evidence at hand to warrant a tentative statement
that it is very rich in tannin or tannin compounds, and that possibly
the quality of resistance is bound up with the nature of this material.

4. THE STRIP CONDITION.--Some of the trees showed the living
bark restricted to a narrow, flattened, rope-like strip running up the
trunk to one or a very few branches (Plate 1, Fig. 3). In these cases
all of the bark was of the callus nature, rich in the resistant
substance, and plentifully besprinkled with small Endothia lesions,