DISEASE OF BLACK OAKS 



115 



Comparatively few instances have yet been recorded 

 where the larger fleshy fungi attack trees by means of in- 

 sect burrows. Probably the best known case is that of 

 Polyporus volvatus * Peck, which has been found by von 

 Schrenk to occur exclusively in the burrows of certain 

 insects. Polyporus pinicola t is also said to enter trees by 

 the same means. Schizophyllum alneum and Lentinus 

 lecomtei have been found by the writer growing in insect 

 burrows in standing trees. Polyporus rimosus is 



men- 



by 



Schrenk i as follows: " Infection takes 



place through the older branches and through the tunnels 

 made by the locust borer." There are undoubtedly many 

 of the Polyporaceae which occasionally enter trees in the 



same manner. 



The writer desires to avail himself of this opportunity 

 to express his thanks to the Director of the Missouri Bo- 

 tanical Garden for the use of the facilities of the Garden 

 in this and other work done by him at the Mississippi 

 Valley Laboratory of the United States Department of 

 Agriculture, located at the Garden. 



* 



EXPLANATION OF PLATES. 



Plate 13. — I, Upper surface of a sporophore of Polyporus obtusus 

 Berk. 2, Lower surface of a sporophore of Polyporus obtusus Berk. 

 The large irregularly shaped pores are well shown. 



Plate 14. — 1, Polyporus obtusus Berk, growing out from the entrance 

 of a burrow of Prionoxystus robiniae in a tree of Quercus marilandica. 

 This tree was but slightly injured by the fungus. 2, Sporophore of 

 Polyporus obtusus Berk, in burrow of oak borer on a tree of Quercus 

 velutina. This and the preceding figure show the general shape of the 

 fungus sporophore very well. 



Plate 15. — 1, Polyporus obtusus on a tree of Quercus marilandica. The 

 tree is but slightly affected in the neighborhood of the insect burrow. 



* von Schrenk, Bull. Div. Phys. &Path., U. S. Dep. Agric. 25:13-14. 



(1900). 



f Spaulding, Report Mo. Bot. Garden. 15: 75-76. (1904). — vonSchrenk, 



Bull, Div. Veg. Phys. & Path., U. S. Dept. Agric. 25: 14. (1900;. 



X von Schrenk, Report Mo. Bot. Garden. 12 : 24. (1901). 



