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

GYROPORUS 33
Context hyphae mostly hyaline as revived in KOH and with thin smooth
walls, as revived in Melzer's lacking colored contents in the region under
the cuticle (the tissue merely yellowish). Clamp connections present but
not numerous.
Habit, habitat, and distribution.-In open hardwoods, rare in
southern Michigan, but apparently more common southward, fruiting
during summer and early fall. The best collection seen to date is that of
Hoseney (1341) made August 5, 1969, in a woodlot in Ann Arbor.
Observations.-This is a very striking bolete in either fresh or dried
condition, but the pigment is unstable in alkali or chloral hydrate.
Kauffman collected it August 15, 1915, and his material was later sent
to Snell. In the University of Michigan Herbarium we have a part of this
collection (an isotype) and the collection by Mrs. Hoseney. Some color
intergradation with G. castaneus is to be expected, particularly in
herbarium specimens in contact with naphthalene. This compound apparently causes a gradual reddening of the dried cap in some of the color
forms of this species. Shaffer 2638 appears to be such a specimen.