13 



PLATE III. 



Fig. 5. — Canker on a black oak 3 inches in diameter showing 

 considerable hypertrophy and also the destruction of tissue 

 to form an open wound. 



Fig. 6. — A young lesion on chestnut oak 1 inch in diameter 

 showing hypertrophy, with characteristic longitudinal crack- 

 ing of the bark. The fungus has completely encircled the 

 trunk. 



PLATE IV. 



Fig. 7. — A canker on a scarlet oak 2.5 inches in diameter show- 

 ing pronounced zonal growth and the stub of a branch at 

 the center. (See Fig. 14 for transverse section through this 

 canker) . 



Fig. 8. — Portion of a small black oak tree 1.5 inches in diameter 

 killed by the diffuse type of the disease. The characteristic 

 fruiting pustules, or sporodochia, are very numerous over 

 the entire surface. 



PLATE V. 



Fig. 9. — Typical Strumella canker on a chestnut trunk 6 inches 

 in diameter. Note that on this species the extent of the 

 lesion is indistinct. 



Fig. 10. — A body canker from a young white oak tree. The 

 elliptical outline of the canker was especially noticeable in 

 its earher stages, and callus-zones mark its progress. 



PLATE VL 



Fig. 11. — Portion of a small black oak tree killed by the Stru- 

 mella disease. Vigorous sprouts or "suckers" were pro- 

 duced below the lesion which was of the semi-diffuse type. 

 - • The center of the infection is marked by a short stub of a 

 branch. 



