Fig. 46.—Piece of oak-bark with fructification of Polyporus 
sulphureus. 
i] | | i 
eA | am 
h ial | 
NM 
z 
\ A 
te Mt zt 
nT 
FiG. 47.—Piece of oak attacked by Polyporus sulphureus, the 
yellowish-white mycelium of which is seen at c andd. (R. Hartig.) 
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