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

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THE BOLETES OF MICHIGAN

Basidia 4-spored, 9-121 broad, clavate, lacking a clamp at basal
septum, content not distinctive in KOH or Melzer's. Pleurocystidia
36-48 X 9-15 /l, fusoid-ventricose, thin-walled, hyaline in KOH and
Melzer's (or some with brown granules when mounted in the latter
medium), readily collapsing and difficult to demonstrate in revived
mounts. Caulohymenium of cells 8-12,u broad, clavate, variable in
length, content hyaline to dingy ochraceous in KOH, no cystidia located
other than the clavate sterile cells.
Pileus cuticle a collapsing trichodermium (the basidiocarps had
been pressed), the end-cells 10-15 g wide with a rounded apex, smooth,
walls lacking incrusting material, content colorless or in some as revived
in Melzer's with bister granules; trichodermial elements 3-5 cells long
usually, cells not appreciably inflated. Context hyphae next to the
cuticle hyaline or nearly so in Melzer's or KOH, walls thin and width
9-15 l. Clamp connections none.
Observations.-It is possibly noteworthy that in the type study
only one possible "amyloid" cell-inclusion was found, and it was of a
doubtful nature. It may be that this species is not distinct from B.
porphyrosporus Fr., but before concluding that it is not it would be
well to have a more critical study of both, in the light of the present
classification, as a basis for conclusions.
Subgenus TYLOPILUS
Stirps ALBOATER
KEY
1. Spores 11-17 M long, 3.5-4.5 (5) t wide.................. T. eximius
1. Spores shorter (9-12 M long)........................ T. alboater
46. Tylopilus eximius (Peck) Singer
Amer. Midl. Nat. 37:109. 1947
Boletus eximius Peck, Jour. Mycol. 3:54. 1887.
Leccinum eximium (Peck) Pomerleau, Bol. Bull. du Cercle des Myc. Amat. de
Qudbec 6:117. 1959.
Boletus robustus Frost, Bull. Buff. Soc. Nat. Sci. 2:104. 1874. (not B. robustus
Fr.)
Pileus 5-12 cm broad, hemispheric, becoming broadly convex to
nearly plane, surface uneven to pitted, dry, unpolished to subtomentose