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

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THE BOLETES OF MICHIGAN

Spores 7-9 (10) X 3-3.5 /u, smooth, pale clay color in KOH but
soon fading to bright yellow singly, more brownish in groups, in
Melzer's "fleeting-amyloid" fresh and as revived pale bister to dingy pale
tan, in face view somewhat boat-shaped, in profile somewhat inequilateral, suprahilar depression fairly distinct, no apical differentiation observed.
Basidia 4-spored, 23-28 X 5.5-7.5 u, clavate, hyaline to yellowish
in KOH, yellowish in Melzer's. Pleurocystidia 36-57 X 7-12 g, narrowly
fusoid-ventricose to subcylindric, hyaline to yellow in KOH and
Melzer's, content not otherwise distinctive in either medium. Cheilocystidia similar to pleurocystidia only smaller and content yellow to
yellow-brown. Caulohymenium in patches near apex and with basidia
and cystidia resembling the cheilohymenial elements.
Tube trama bilateral, the divergent hyphae gelatinous, sections
mounted in Melzer's and crushed becoming dark greenish to bluish green
as seen under the microscope (but no localized amyloid reaction
present). Cutis of pileus if interwoven hyphae 4-8 u wide, yellowish in
KOH and with end-cells tubular to narrowly clavate, the walls showing a
slight tendency to become roughened as in Leccinum insigne.
Context hyphae hyaline in KOH, thin-walled, much-branched,
interwoven, yellowish to yellowish hyaline in KOH and a dingier more
yellowish brown in Melzer's but content not distinctive as single cells are
viewed. Clamp connections absent.
Habit, habitat, and distribution.-Gregarious in an oak woods, Otis
Lake, Barry County, August 19, 1966, collection S. Mazzer (Smith
73092).
Observations.-This species differs from B. piperatus in the fleetingamyloid reaction of the spores when fresh, the "fleeting-amyloid" (unlocalized) reaction noted in the revived tube tissue, in the slowly only
somewhat peppery taste, the blue staining of freshly injured basidiocarp
tissue, and the dull-colored pileus context.
Section PSEUDOBOLETI (Singer), comb. nov.
Xerocomus section Pseudoboleti Singer
Farlowia 2:299. 1945
In addition to the species keyed here see B. subilludens and B.
alutaceus.