54 THE POLYPORAOEAE OF WISCONSIN. 



Poria vaporaria (Pers.) Fries. 



Effused, innate, the white flocculent mycelium creeping in the wood ; 

 pores large, angulate, whitish-pallid, crowded in a firm persistent stra- 

 tum. 



This is one of the thinnest of our white Porias. The pileus is often 

 so thin that it appears as if the pores grow directly from the substra- 

 tum. The pores are comparatively large, irregular, shallow, seldom 

 more than 1 mm. deep, the dissepiments often breaking down. The in- 

 nate myclium starts in little patches here and there. 



Not very common. A few small specimens have been found at Madi- 

 son on fallen oak branches and at Horicon and Bangor. The color 

 changes to cream on drying. 



Hartig, in his work on timber diseases, classes this with the most 

 destructive forms, regarding it as the cause of a sort of "dry rot" of 

 pine timber and as infecting also the trees themselves. 



Our specimens measure about 7 to 8 cm. long, and 2 cm. wide. The 

 pores usually not more than 1 mm. in diameter. 



The species differs from Poria papyracea Schweinitz, and Poria 

 macer Som., in its habitat rather than in any very definite morphologi- 

 cal characteristics. The former is found on dead Vitis, the latter on 

 Populus. P. papyracea is also somewhat thinner than either of the 

 others. 



Poria corticola Fr. 



Very broadly effused, equable, firm, white or pallid; mycelium in- 

 terwoven into a subcoriaceous stratum. Pores naked, superficial, com- 

 monly obsolete, punctiform. 



Not common. Found on oak wood in Madison. One specimen 

 partly covers a decaying Nummularia. The largest is about 14 cm. 

 long, 4.5 cm. wide and scarcely 1 mm. thick. When young it is easily 

 separable. The whitish margin is thin and tends to become refiexed. 

 The pores are small and shallow at first and appear to be merely ir- 

 regular depressions. Later they lengthen somewhat and then become 

 torn so as to resemble an Irpex, or an old Poria sinuosa, but are harder 

 and more brittle. 



The specimens agree well with no. 1014 Fungi Columbiani and no. 

 3002 North American Fungi. This species is supposed by Morgan to 

 include the following, which differ perhaps only in the degree of evo- 

 lution of the substerile pores and the substratum on which they grow : 

 (a) Poria populim ; (b) P. faginea; (c) P. quercina (Pers., Myc. Eur., 



