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

LECCINUM

145

tapered, the content yellow to orange-buff in KOH (in young pilei distinctly reddish), in Melzer's the content orange-brown and forming
globules of various sizes often filling the cells. Context hyphae hyaline
in Melzer's. Clamp connections absent.
Habit, habitat, and distribution.-Scattered under pine and aspen,
not uncommon during summer and fall throughout the state where
aspen and pine grow.
Observations.-As we have observed this species in Michigan the
cuticular hyphae are relatively smooth in contrast to those of L. insigne,
which is our common species under aspen in June and July. In L.
insigne the stipe is ornamented with black points and squamules by
maturity, whereas in L. aurantiacum it is not uncommon to find basidiocarps with the stipe nearly white when half expanded and with the
ornamentation becoming orange-tan or more reddish before finally going
to black. In Michigan it is not limited to a single tree-associate.
69. Leccinum subrobustum Smith, Thiers, & Watling
Lloydia 31:261. 1968
Pileus 6-12 cm broad, broadly convex to convex, in age nearly
plane; surface dry at first and more or less distinctly appressed-fibrillose,
in age nearly glabrous and subviscid, at times becoming distinctly fibrillose-squamulose; color dark rusty orange ("burnt-sienna" to "Sanford's
brown"), paler to the ochraceous-orange margin; margin appendiculate.
Context pallid when cut but soon tinged reddish cinnamon and then
slowly changing to fuscous, odor and taste not distinctive, the FeSO4
reaction olive blackish finally.
Tubes white to pallid, depressed around the stipe, slowly becoming
wood-brown to sepia; pores minute, staining olive if lightly bruised and
olive-brown when severely bruised but stains eventually fuscous.
Stipe 9-12 (15) cm long, 1-3 cm thick at apex, enlarged downward, solid, pallid within when cut but soon staining reddish cinnamon
and finally fuscous, in the lower part often stained blue and/or deep red
also; surface ornamented at first with reddish to reddish brown squamules which by maturity are usually blackish, ornamentation rather
coarse.
Spore deposit olive to olive-brown, olive-brown as air-dried; spores
13-16 X 4-5 t, smooth, wall 0.5 / thick, apex with a thin spot but no
true pore; shape in face view subfusiform, in profile elongate-inequilateral; color dingy ochraceous to brownish ochraceous in KOH; in
Melzer's ochraceous to weakly dextrinoid.