Pileus 5-10 cm latus, convexus vel pulvinatus, siccus, glaber, subbrunneus vel bubalinus, tactu fusco-brunneus. Contextus 1-1.5 cm crassus, albus vel avellaneus, immutabilis vel tarde brunnescens. Tubuli 0.8-1.5 cm longi, albi vel pallidi demum bubalini vel vinacei, tactu brunnei. Stipes 4-9 cm longus, 1.5-2.5 cm crassus, glaber vel pruinosus, non reticulatus, albus, tactu vinaceus vel brunneus. Sporae 8.6-11.4 X 3.3-4 Ám, subfusoideae vel cylindricae. Cuticula intertexta. Holotypus (no. 6177) a Joseph Ammirati, Jr., lectus prope Mount Shasta, Shasta County, November 21, 1971; in Herbarium San Francisco State University conservatus.

Pileus 5-10 cm broad, convex to pulvinate, sometimes becoming undulating and uneven with age; surface dry to "sticky" but not truly viscid; color pale vinaceous-brown to buff ("pale purplish vinaceous" to "light vinaceous-fawn" to "pale vinaceous-pink" to "tilleul buff"), with age often drab ("vinaceous-drab" to "brownish drab"), brown to ochraceous colors appear on exposed pilei, changing to dark brown ("olive-brown" to "buffy brown" to "wood brown") when bruised, glabrous to occasionally obscurely velutinous; margin entire, sometimes with a slight sterile border. Context 1-1.5 cm thick, white to drab ("pale olive-buff" to "vinaceous-drab"), unchanging or sometimes slowly becoming pale brown when exposed. Taste and odor mild.

Tubes 0.8-1.5 cm long, depressed with decurrent lines extending down the stipe for 2-3 mm, white to pallid when young, becoming buff to vinaceous ("avellaneous" to "light vinaceous-fawn" to "vinaceous-buff") with age, changing to brown ("vinaceous-buff" to "wood brown") when bruised; pores one to two per millimeter, irregular to somewhat rounded, concolorous.

Stipe 4-9 cm long, 1.5-2.5 cm thick, equal to tapering downward, occasionally with a slightly enlarged base, solid; surface dry, glabrous to scurfy-pruinose, not reticulate, or only obscurely so for 1 cm at the apex resulting from decurrent tubes; color white, staining vinaceous to brown ("avellaneous" to purple-drab" to "blackish purple") when bruised. Context white or mottled with pale brownish spots, changing to brown when exposed.

Spore print color not determined. Spores (7.5)8.6-11.4(13.6) X 3.3-4 Ám, subfusoid to cylindric, inequilateral, hyaline to very pale ochraceous in KOH, ochraceous to dextrinoid in Melzer's, walls smooth, thin.

Basidia 20-25 X 5-8 Ám, clavate, hyaline, staining cinnamon on the pores, four-spored. Hymenial cystidia 45-69 X 5-10 Ám, scattered to numerous, often very obscure, clavate to irregular in outline, hyaline in KOH, bright rust ochraceous in Melzer's.

Tube trama divergent from a distinct central strand, gelatinous, hyaline except for the pale ochraceous color of the strand, hyphae 5-7 Ám wide. Pileus trama interwoven, hyaline in KOH, homogeneous. Pileus cuticle differentiated as in interwoven to tangled trichodermium, no pileocystidia, ochraceous in KOH and Melzer's, hyphae 3-5 Ám wide. Stipe cuticle interwoven with no basidia or caulocystidia. Clamp connections absent.

Chemical reactions KOH-cuticle brown to brownish ochraceous, context dull light yellow; FeS04-context dull bluish green.

Habit, habitat, and distribution Scattered to gregarious in soil under oaks. Known only from the Mount Shasta area in Shasta County.

Material studied Shasta County: Ammirati 6177 type; Thiers 28569 (collection made by Joseph Ammirati).

Observations This species belongs to the same complex as T. indecisus and T ferrugineus. Tylopilus ammiratii appears much more closely related to T indecisus; however, T. indecisus has a reticulate stipe, a considerably darker colored pileus and stipe, longer spores, and a fertile, cellular cuticle on the stipe. Both species occur under oaks, but T. indecisus is known only from under valley oaks, whereas T. ammiratii has been found only under California black oak. Tylopilus ferrugineus is distinguished by the very dark brown color of the pileus and the smaller pores.

Edibility unknown.

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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