2. EXTENSION OF THE CALLUS TISSUE.--In many cases the callus tissue is of considerably greater extent than the normal area one would expect around a wound. It may even occur that the whole inner bark around the trunk is of a callused nature, without any open cankers showing at all. For example in a tree of which I have a photograph here (Figs. 2 and 4), the outer bark is sloughing off, revealing callused bark underneath of entirely different appearance, which no one would recognize as chestnut bark. This particular tree photographed represents an extreme in this respect. It seemed as if the whole tree was getting a new kind of bark, and yet this same character appears in all of the highly resistant trees. On cutting into this new callused inner bark it was found plentifully dotted with tiny _Endothia_ lesions, which however, never penetrated deeply. (Fig 4). Close to the cambium the white 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.]