SUILLUS PONDEROSUS Smith and Thiers, Contr. Toward a Monogr. of N. Am. Sp. of Suillus, p. 38. 1964

Illustrations: See Microfiche No. 45
Smith, A. H., and H. D. Thiers, A Contribution Toward a Monograph of North American Species of Suillus pl. 11.

Pileus 9-25 cm broad, convex when young, becoming plane to irregular with age; surface glabrous or with scattered veil remnants near the margin, viscid to glutinous, somewhat streaked beneath the gluten; color reddish to dark brownish lavender ("vinaceous-brown" to "testaccous") to sometimes brown ("cinnamon") or yellow toward the margin and streaked with cinnamon; margin appendiculate from veil remnants. Context 2-3 cm thick, firm, yellow, unchanging or becoming pale vinaceous in spots. Taste mild; odor mild or acidulous.

Tubes up to 1.5 cm long, decurrent, dull yellow, unchanging when exposed; pores large, 1-3 mm in longest dimension, subangular, yellow, staining brownish.

Stipe 9-14 cm long, 3-6 cm thick, tapered toward the base, often pinched, solid; surface reticulate above the annulus from decurrent tubes, sometimes obscurely reticulate below the annulus, bright yellow above annulus, sordid rust brown when handled; annulus orange to white, membranous, superior, often stained reddish cinnamon on underside by a gelatinous layer. Context pale yellow throughout, greenish in base when exposed, with a faint pink tinge toward the apex.

Spore print brown. Spores 8-10 X 3.8-5 Ám, hyaline to olive yellow in KOH, pale ochraceous in Melzer's, in face view ellipsoid to subfusoid to oblong, in side view somewhat inequilateral, smooth, thin-walled.

Basidia 26-31 X 7-10 Ám, four-spored, clavate, hyaline in KOH. Hymenial cystidia 29-72 X 5-8 Ám, solitary or clustered with dark yellow-brown pigment in and around the base, cylindric to clavate, or crooked, at times subfusoid, hyaline or with dark-brown pigment as revived in KOH.

Tube trama hyaline, gelatinous, somewhat divergent, hyphae 6-8 Ám wide. Pileus trama interwoven, homogeneous, scattered laticifers present. Pileus cuticle a gelatinous layer of interwoven, hyaline hyphae, 2-4 Ám wide, pale ochraceous in KOH. Clamp connections not seen.

Chemical reactions KOH-cuticle black, tubes black, context vinaceous; NH4OH-context pale lavender, tubes lavender; HNO3-tubes pale orange; H2SO4-context yellow, tubes red; FeSO4-context and tubes gray.

Habit, habitat, and distribution Scattered to cespitose in soil under Douglas fir in coastal forests of northern California.

Material studied Marin County: Madden 693, 780, 869; Thiers 10040, 18124. Mendocino County: Peters 174, 214; Thiers 8163, 8207, 8279, 8382, 8472, 8612, 8762, 8776, 8785, 8821, 8867, 8874, 9242, 9251, 9284, 9338, 9354, 10531, 10570, 14107, 14143, 14144, 14610, 17899, 21511, 23081. Napa County: Thiers 11897, 21808. Santa Cruz County: 17941. Sonoma County: Motta 94.

Observations This is the largest species of Suillus known from California, with some pilei measuring up to 25 cm in diameter. Smaller-sized basidiocarps, however, are much more commonly found. Suillus ponderosus is further characterized by the bright-reddish-brown color of the pileus, the glabrous surface of the pileus, and the viscid to glutinous annulus, which is bright orange to orange yellow in young basidiocarps. This species appears most closely related to S. caerulescens, and they both form mycorrhizal associations with Douglas fir. Older basidiocarps of the two species are similar in appearance; however, younger developmental stages can be separated by using the characters enumerated above.

Edible.

The Boletes of California
Copyright © 1975 by Dr. Harry D. Thiers
Additional content for the online edition © 1998 by Michael Wood, Fred Stevens, & Michael Boom
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