The boletes of Michigan, by Alexander H. Smith and Harry D. Thiers.

BOLETUS

223

5. Pileus dark to bright red when young; tubes yellow and pores staining
blue (often slowly) when bruised (but see B. carminipes also).. Subsect. Fraterni
5. Pileus differently colored when young........................ 6
6. Pores staining greenish to blue when injured (often slowly)................................ Subsect. Subtomentosi
6. Pores staining yellow to brownish or unchanging when bruised................................. Subsect. Versicolores
Subsection SULPHUREI (Singer), comb. & stat. nov.
Phlebopus section Sulphurei Singer
Amer. Midl. Nat. 37:2. 1947
Stirps SPHAEROCEPHALUS
114. Boletus sphaerocephalus Barla
Champ. Nice p. 72. 1859
Ixocomus sphaerocephalus (Barla) Quelet, Flore Mycol. Fr. p. 419. 1888.
Illus. PI. 92.
Pileus 5-10 cm broad, convex with a curved-in irregular margin,
expanding to broadly convex or nearly plane; surface soft and subviscid
to tough but no gelatinous layer present, unpolished to subtomentose,
in age at times areolate; color evenly sulphur-yellow overall but on aging
slowly fading to pallid; veil lacking. Context thick, sulphur-yellow under
the cuticle, paler inward, turning blue when cut, with FeSO4 no reaction, taste mild to bitterish, odor slight.
Tubes adnate becoming depressed around the stipe, pale sulphuryellow when young, when injured staining blue, 10-15 mm deep; pores 2-3
per mm when young, broader at maturity, staining blue and then slowly
brownish where injured.
Stipe 6-10 cm long, 1-2.5 cm thick (or larger in giant basidiocarps), central to eccentric, narrowed to a point below, solid, yellow
within, surface yellow and unpolished (appearing somewhat mattedfibrillose), yellow tomentum and mycelium usually holding much debris
around the base.
Spore deposit olive brownish or tinged ochraceous in the olivebrown range; spores 7-9 X 3-3.5,u, oblong to ellipsoid, walls slightly
thickened, smooth, lacking an apical pore, dull ochraceous in Melzer's,
bright yellow in KOH.