14 



PLATE VII. 



Fig. 12. — A black oak which has been broken by the wind at 

 the lesion. The copious sprouting below the lesion is evi- 

 dent and the canker also shows the work of woodpeckers. 



PLATE Vm. 



Fig. 13. — Transverse section through the middle of the canker 

 shown in Fig. 3. The light area on the left is the only 

 normal tissue that remains. 



Fig. 14. — Transverse section through the middle of the canker 

 shown in Fig. 7. The lighter area above the organic center 

 has been invaded by the fungus and the wood disintegrated. 

 This afifected wood is soft and punky. 



PLATE IX. 



Fig. 15. — An isolation culture oi Btrumella coryneoidea on 3% 

 dextrose agar, made by tissue transfers. The small frag- 

 ment of diseased tissue is still noticeable at the center of 

 each colony. 



Fig. 16. — An isolation culture of Strumella coryneoidea on 3% 

 dextrose agar made by transferring marked colonies from 

 poured plates. 



PLATE X. 



Fig. 17. — A series of cultures of Strumella on dextrose agar 

 taken from the under surface to show the variation in the 

 development of the black coloration characteristic of the 

 species. Each culture represents a different strain. 



PLATE XL 



Fig. 18. — A piece of bark slightly magnified to show the char- 

 acteristic fruiting pustules, or sporodochia, in the form of 

 dark brown, powdery, erumpent nodules. 



