THALLOPHYTES: FUNGI 
287 
has a stalk-like portion, the stipe, at the base of which the 
slender mycelial threads look like white rootlets ; and an 
expanded, umbrella-like top called the pileus. From the 
under surface of the pileus there hang thin radiating plates, 
or gills (Fig. 255), Each gill is a mass of interwoven fila- 
ments (hyphae), whose tips turn toward the surface and 
form a compact layer of end cells (Fig. 256). These end 
FIG. 260. A bracket fungus (Polyporus) growing on the trunk of a red oak. 
CALDWELL. 
cells, forming the surface of the gill, are club-shaped, and 
are called basidia. From the broad end of each basidium 
two or four delicate braiiches arise, each bearing a minute 
spore, very much as the sporidia appear in the wheat rust. 
