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

GYROPORUS Qu4let
Enchir. Fung. p. 161. 1886
The short, ellipsoid spores which are yellow in a deposit and the
hollow stipe at maturity characterize this genus. A veil may or may not
be present. The pores are small and nearly circular in outline. The cuticle of the pileus may be a trichodermium or a cutis of appressed fibrils.
Type species: Gyroporus cyanescens Fries.
KEY TO SPECIES
1. Context of pileus instantly changing to blue to lilaceous to deep violet
when cut......................... G. cyanescens var. violaceotinctus
1. Context not changing to blue or violet readily......................2
2. Pileus mineral red to dark vinaceous-red.............. G. purpurinus
2. Pileus rusty to chestnut-brown, tawny or crust-brown...... G. castaneus
1. Gyroporus cyanescens (Fries) Quelet
Enchir. Fung. p. 161. 1886
var. violaceotinctus Watling
Notes from Royal Bot. Garden, Edinb. 29(1): 63. 1969
Illus. P1. 1.
Pileus 4-12 cm broad, obtuse to convex, becoming broadly convex,
sometimes nearly plane or shallowly depressed; margin thin, frequently
splitting, incurved when young, entire; surface dry, uneven to pitted or
wrinkled, appressed fibrillose, ground color pale straw color ("light
buff') or occasionally near cinnamon-buff, entire basidiocarp often
staining blue when old, fibrils and squamules occasionally cinnamon-buff
to clay color. Context thick, (10-15 mm), brittle, pallid but instantly
indigo-blue when cut or broken, odor and taste not distinctive.
Tubes pallid (white to "ivory-yellow") at first, gradually pale
olive-yellow ("Naples-yellow" to "seafoam-yellow") with age (bright
yellow becoming pallid), instantly indigo-blue where injured, deeply depressed around the stipe, 5-10 mm deep; pores small and round, about 2
per mm, instantly indigo blue when bruised.
Stipe 4-10 cm long, 1-2.5 cm thick at apex, usually enlarged
downward and 2.5-3.5 cm thick at base, occasionally clavate, frequently
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