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

SUILL US

63

Observations.-This species is very close to the common S. americanus, but has a thicker stipe (commonly up to 15 mm), the stipes are
often hollowed somewhat at the base and not infrequently furnished
with an annulus. In the Michigan collections the colors are about the
same as those of S. americanus, but see Smith, Thiers, & Miller (1966).
21. Suillus americanus (Peck) Snell ex Slipp & Snell
Lloydia 7:39. 1944
Boletus americanus Peck, Bull. N. Y. State Mus. 1:62. 1887.
Illus. Figs. 31, 34; P1. 25.
Pileus 3-10 cm broad, obtuse with an incurved margin, expanding
to broadly convex or with a low obtuse umbo; margin with soft cottony
veil material appendiculate or continuous all along it, the veil yellowish
but in age the collapsed patches brownish; surface bright yellow, viscid,
with scattered appressed patches of fibrils buff to dingy cinnamon and
variously distributed, at times streaked with reddish fibrils in places but
veil never red, rarely with reddish spots. Context mustard-yellow, staining vinaceous-brown when cut, odor and taste not distinctive.
Tubes 4-6 mm deep, adnate to decurrent, dull yellow and staining
vinaceous-brown where injured; pores large and often angular (up to
1.5-2 mm in diameter), mustard-yellow when young, duller ochraceous
in age, drying dark yellow-brown.
Stipe 3-9 cm long, 4-10 mm thick, equal, often crooked, becoming hollow, cortex yellow, lacking salmon tints; surface lemon-yellow
and covered with glandular dots which darken to "cinnamon-buff" or
browner in age or from handling, surface generally vinaceous-brown
where handled; annulus lacking, the material of the false veil seldom if
ever touching the stipe.
Spore deposit dull cinnamon; spores 8-11 X 3-4 p, narrowly and
obscurely fusiform in face view, in profile narrowly inequilateral, dingy
yellow to brownish in KOH, smooth, weakly dextrinoid (pale cinnamon
in Melzer's).
Basidia 17-22 X 5-7 uL, 4-spored, clavate, yellowish to hyaline in
KOH, yellowish in Melzer's. Pleurocystidia in fascicles surrounded by
amorphous bister-brown pigment as revived in KOH; subcylindric to
clavate or obventricose, 36-60 X 7-11,j, content hyaline or dark brown.
Cheilocystidia abundant along the dissepiments, hyaline to brown, 40-65
X 7-12 t, cylindric, clavate or fusoid-ventricose, with a great deal of
dark brown amorphous pigment at the level of the hymenium when