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

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THE BOLETES OF MICHIGAN

Spores 14-18 (20) X 5-6.5 (8),, smooth but with a tendency to
be angular, with a minute thin spot at apex, shape in face view fusoidventricose, in profile strongly inequilateral and usually with a deep
suprahilar depression. Color in KOH pale snuff-brown, in Melzer's reddish tawny (dextrinoid), wall about 0.3-0.5 p thick.
Basidia 4-spored, 8-11 p broad, hyaline in KOH and readily gelatinizing. Pleurocystidia rare, 30-42 X 7-12 p, fusoid-ventricose with
obtuse to subacute apex, hyaline in KOH and Melzer's or content
weakly ochraceous and homogeneous, thin-walled, walls smooth. Cheilocystidia subventricose to narrowly fusoid-ventricose or mucronate, 16-26
X 4-9 p, usually yellowish in KOH or Melzer's. Cailocystidia clavate to
somewhat cystidioid, 33-50 X 6-14 p, content ochraceous in KOH,
thin-walled, wall smooth.
Tube trama of the Boletus subtype, inamyloid under the microscope but with a strong fleeting-amyloid reaction when the trama is
crushed in Melzer's. Pileus cutis of long narrow tubular hyphae 2.5-5 p
wide, with thin smooth walls (in either KOH or in Melzer's) and ochraceous content, end-cells elongate with the tips blunt or slightly tapered,
no short or inflated cells present, the end-cells not forming a palisade.
Hyphae of the subcutis and context mostly ochraceous in KOH. Clamp
connections none.
In the type collection insects have destroyed most of the cuticle
of the pileus, but there is some evidence to indicate the pileus was
yellow as dried. The hairs at the base of the stipe dried very dark red.
The diagnostic features of the type are: (1) wide decidedly inequilateral
spores, (2) hairs at base of the stipe which are red as dried, (3) white
flesh of the pileus before it changes to blue, (4) yellow tones in the
pileus when young. The following is a description of Michigan collections which have been placed here.
Pileus 6-13 cm broad, convex to nearly plane to occasionally obscurely umbonate becoming broadly convex to plane, margin even or
slightly wavy; surface dry and dull, minutely fibrillose under a lens to
velvety-tomentose, with age the cuticle becoming areolate and the
areolae tomentose to minutely fibrillose-squamulose, color often
"tawny" to "rufous" to "cinnamon-rufous" with a yellow to orangeyellow ("antimony-yellow" to "pale orange-yellow") margin, color soon
changing to dark blue to blackish when bruised or on aging. Context
moderately thick, soft, bright yellow ("baryta-yellow" to "sulphuryellow") but changing to blue so quickly when cut that original color is
easily missed, odor none, taste mild to slightly acid.