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

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THE BOLETES OF MICHIGAN

elongate (and then often dumbbell-shaped) cells hyaline in KOH and
with minutely ornamented walls, terminal cells globose to elongate or
dumbbell-shaped, all thin-walled; hyphae beneath the trichodermium
with dextrinoid incrusting material in addition to patches of purplish
vinaceous debris between the cells. Hyphae of upper context merely
yellow in Melzer's. Clamp connections absent.
Habit, habitat, and distribution.-Gregarious on an old conifer log,
Douglas Lake, Cheboygan County, July 1, 1968, Smith 75435.
Observations.-This species has the stature of Tylopilus gracilis but
belongs near B. subtomentosus. From the variety perplexus of that
species it differs in the dull yellow-brown pruina on the stipe, lack of a
change to blue when injured, having purple-vinaceous debris between the
cells of the trichodermium in mounts in Melzer's, and in having bright
yellow mycelium at the base of the stipe. The small pores are the best
field character, but one must be careful to compare mature specimens.
129. Boletus minutiporus Smith & Thiers, sp. nov.
Illus. P1. 101 (lower).
Pileus 4-6 cm latus, late convexus, siccus, subtomentosus, sordide
olivaceus, demum ochraceus. Contextus pallide luteus tactu tarde subcaeruleus. Tubuli 5-7 mm longi, adnati vel subdecurrentes, pallide lutei;
pori pallide lutei. Stipes 3.5-6 cm longus, 9-14 mm crassus, demum
cavus, deorsum luteo-myceliosus, sursum subluteus. Specimen typicum in
Herb. Univ. Mich. conservatum est; prope Mackinaw City, Emmet
County, July 4, 1968, legit H. D. Thiers (Smith 75467).
Pileus 4-6 cm broad, convex becoming broadly convex, surface dry
and subtomentose, dull olive-buff ("deep olive-buff") becoming ochraceous in drying, margin even. Context pallid to very pale yellow, with a
brownish line under the cuticle, when injured slowly staining greenish
blue, NH4OH on cuticle dingy olive then quickly brownish; FeS04 no
reaction on context.
Tubes rather shallow (5-7 mm deep), adnate to short-decurrent,
pale wax-yellow and unchanging when cut; pores small 1.5-2.5 per mm,
round; "Naples-yellow" (pale yellow) and unchanging when bruised.
Stipe 3.5-6 cm long, 9-14 mm thick, nearly equal, pallid within,
becoming hollow in midportion; surface yellow below, pale dingy cinnamon above from a faint pruinosity, basal mycelium pale sulphuryellow, not discoloring when handled.