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

TYLOPIL US

101

age; surface dry and velvety, soon becoming conspicuously rimoseareolate, the pale context showing in the cracks; color olive-brown to
dark dingy yellow-brown (olive-brown) to "Prout's brown," in age the
context as exposed in the cracks pale watery green. Context thick and
firm, yellowish white, slowly staining pale bluish green where cut, dingy
vinaceous around the larval tunnels, often staining vinaceous gray slowly
where cut (after the green has faded); odor pungent and peculiar but
not strong, taste mild to slightly acidulous; KOH causing a vinaceousgray color, and in FeSO4 a greenish to bluish tint develops.
Tubes adnate to depressed or in age decurrent, 1-2 cm deep, grayish to olive-gray at first, chocolate color in age, staining blue and then
darker brownish where injured; pores 1-2 per mm, isodiametric or nearly
so, grayish at first, where injured becoming chocolate.
Stipe (2) 3-6 cm long, 10-15 mm at apex, equal or nearly so,
solid, blue in the cortex in apical region when cut, reddish in base but
slowly changing to brownish, in the central part slowly staining vinaceous when first cut; surface faintly brownish pruinose to unpolished,
nearly concolorous with pileus but with a copper-blue zone at apex,
whitish at base.
Spore print "benzo-brown" (purple-brown) in a good fresh deposit, nearer wood-brown when faded; spores 11-15 X 5-6.5 (7)ix, in
profile inequilateral with a distinct suprahilar depression, in face view
narrowly to broadly boat-shaped or narrowly ovate to nearly oblong but
most often broadly ovate, in profile subelliptic to somewhat inequilateral, smooth, wall slightly thickened; dark dingy yellow (near bister) as
revived in Melzer's, in KOH pale dingy yellow-brown.
Basidia 22-35 X 9-15 gu, 2- and 4-spored, broadly clavate. Pleurocystidia rare to scattered, 50-60 X 9-15 iu, fusoid-ventricose, smooth,
thin-walled, content smoky brown in some as revived in KOH, as revived
in Melzer's with a dextrinoid content or some showing a content of dark
blue granules (amyloid). Cheilocystidia mostly basidiole-like and smoky
ochraceous in KOH but finally greatly inflated.
Tube trama of long cylindric cells up to 15 ji in diameter, in a
main strand and some diverging toward the subhymenium on either side
as seen in a longitudinal section (Boletus subtype). Cuticle of pileus a
trichodermium of septate hyphae 8-18 u in diameter, the end-cells usually somewhat cystidioid, the lower cells often short and somewhat inflated, as revived in Melzer's the elements with dark yellow-brown pigment in the cells and some with incrusting pigment granules, paler and
dull ochraceous in KOH. Clamp connections absent.
Habit, habitat, and distribution.-Solitary to gregarious or rarely in
small clusters, on sandy open soil in thin oak woods, or on exposed soil