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

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THE BOLETES OF MICHIGAN

Tubes pale lemon-yellow and beaded with drops when young (yellow in distinct contrast to pileus context), dingy ocher-yellow in age;
pores dingy yellow, very minute (2-4 per mm), slowly brownish where
bruised.
Stipe 5-12 cm long, 6-14 mm thick, equal, solid, surface sticky
when fresh from exuded drops, with distinct glandular dots showing
when mature, whitish at first, then pale pinkish buff, staining dingy
olive to brownish over basal area when handled. Annulus thin and
evanescent, cottony to the inside; interior of stipe orange-buff throughout, no olive line in the base as seen in a longitudinal section, with
copious white mycelium around the base.
Spore deposit dull cinnamon becoming pale cinnamon when airdried; spores 7-9 X 2.8-3.2 g, smooth, in face view suboblong to subfusoid, in profile view narrowly inequilateral, the suprahilar depression
broad, yellowish hyaline in KOH, mostly pale tawny in Melzer's.
Basidia 4-spored, 18-23 X 5.5-7,i, narrowly clavate, hyaline in
KOH, yellowish in Melzer's. Pleurocystidia 40-60 X 5-8,, subcylindric
to narrowly clavate, mostly with dark yellow-brown content revived in
KOH and with amorphous incrusting material around the base of the
cluster, in Melzer's the incrusting material partially dissolving to form
pigment globules. Cheilocystidia in bunches and similar to pleurocystidia
but more amorphous incrusting material present in the subhymenial tissue. Caulocystidia 25-38 X 5-7 u, scattered to bunched in the caulohymenium which is heavily incrusted with dark brown amorphous material in KOH.
Tube trama of gelatinous-refractive hyphae diverging from a very
poorly formed central strand. Pileus cutis a thick layer of interwoven
gelatinous hyphae 3-8 I wide, the cells of the hyphae tubular and
hyaline in KOH, and in Melzer's yellowish. Context hyphae hyaline in
KOH, in Melzer's with homogeneous orange-yellow content, 5-12,
wide, thin-walled and lacking wall incrustations. Clamp connections
absent.
Habit, habitat, and distribution.-Gregarious under red pine (P.
resinosa), City Park, Midland, September 4, 1966. Smith 73307.
Observations.-Our account (1964) of this species under var. acidus
applies to a pale yellow species with brown tube mouths when young.
This was a mistake. The Midland collection clearly demonstrated that
there is a white, annulate, strongly acid taxon, and it must be regarded
as the type variety of Peck's species. Like S. placidus, the pilei become
pale yellow in age. The species in its typical form was very abundant in
the park at Midland on the date cited. The taxon described by Snell
Singer, & Dick (1959) under this name is very likely a composite description covering several closely related taxa.