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

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(viscid to slimy to the touch when wet and staining the fingers yellowCoker), color evenly chocolate-brown at all stages or a purplish tone
evident, with a distinct bloom at first, margin sterile. Context 1-2 cm
thick, firm, pallid to avelIaneous or with more purplish tints, becoming
dark around the wormholes ("odor of rotting wood or rancid oil and
taste similar" or "bitterish"-Coker).
Tubes 10-17 mm deep, dark brownish purple (darker than the
context of the pileus), depressed or at times nearly free; pores small
(about 3 per mm), dissepiments thick, stuffed when young, concolorous
with pileus or more purplish, not changing readily when bruised but
nearly black in age.
Stipe 4.5-9 cm long, 1-3 cm thick, straight or curved, equal or
enlarged upward, often somewhat compressed, solid, colored like the
surface, surface about concolorous with the tubes and furfuraceouspunctate, the particles of roughness purplish, even or at times longitudinally striate to grooved.
Spore deposit reddish brown to more vinaceous. Spores 11-17 X
3.5-5 i, narrowly subfusoid in face view, in profile narrowly inequilateral with a broad suprahilar depression, smooth, wall thickened somewhat,
dingy yellowish in KOH, dingy tan to dull rusty brown in Melzer's.
Basidia 23-30 X 7-9 u, 4-spored, clavate. Pleurocystidia scattered,
27-42 X 8-12 u, fusoid-ventricose, thin-walled, in KOH and Melzer's
with a dingy yellow wrinkled content similar to that in many basidia.
Cheilocystidia 20-30 X 7-8 g, narrowly fusoid, yellowish to hyaline in
KOH.
Cuticle of pileus a trichodermium of hyphae 3-6 u wide, the cells
greatly elongated (septa sparse), in KOH and Melzer's the content mostly dingy ochraceous to pale bister when revived, end-cells mostly cylindric to clavate and obtuse, thin-walled, with much pale tawny intercellular debris in Melzer's. Clamp connections absent.
Habit, habitat, and distribution.-This species has been reported
from Michigan, but all the collections we have located were misidentified. As for T. alboater, we expect that it does occur here and for that
reason include it.
Observations.-A specimen of B. robustus Frost on deposit in the
Peck collections at Albany has been studied. It has the typical elongate
narrow spores nearly hyaline to dingy yellowish in KOH and the somewhat dextrinoid content in Melzer's which feature Peck's collections.
The microscopic data in our description are from a collection by
Snell August 24, 1937, near Reading, Vermont. Concerning whether or
not the species should be placed in Leccinum, we can only say that the
color of the stipe ornamentation is merely a reflection of the color of