GASTROBOLETUS AMYLOIDEUS Thiers, Brittonia 21:251. 1969

Gastrocarp 4-8 cm broad at maturity, convex to broadly convex when young, becoming flattened to depressed to plano-convex at maturity; surface dry, dull, glabrous to subtomentose during all stages of development; color yellow ("colonial buff" to "old gold") to buff or rust brown ("ochraceous-buff" to "ochraceous-tawny"), or with reddish areas scattered throughout. Context 1-2 cm thick, pale yellow, unchanging when exposed. Taste and odor not distinctive.

Gleba tubulose, tubes 1-2.5 cm long, highly disoriented and appearing to radiate at various angles from the peridium, characteristically yellow ("colonial buff" to "chamois") during all stages of development, unchanging when bruised or exposed; pores small, less than 1 mm broad, concolorous with the tubes to occasionally reddish.

Stipe-columella 1-2 cm long, 0.5-1.5 cm thick, very reduced and sometimes apparently lacking, solid; surface dry, dull, glabrous, yellow ("chamois" to "old gold" to as pale as "warm buff") during all stages of development, with a characteristic red band at the apex. Context yellow, unchanging upon exposure.

Spores 13.5-18.8 X 6-7 Ám, brown in KOH, strongly amyloid when seen in mass in Melzer's, fusoid to subcylindric, thick-walled, smooth, sterigmata terminal.

Basidia 26-32 X 7-10 Ám, hyaline, clavate, four-spored. Hymenial cystidia apparently not present.

Tube trama hyaline, weakly divergent, at least in young gastrocarps. Peridial trama up to 15 Ám broad, interwoven, septations in Melzer's becoming conspicuous and giving either a dextrinoid or amyloid reaction. Cuticle of upper peridium interwoven to tangled, pale ochraceous to dark yellow in KOH and Melzer's, hyphae 5-7 Ám wide. Clamp connections absent.

Habit, habitat, and distribution Hypogeous under lodgepole pine and red fir in higher elevations in Sierra Nevada in California. Collected in late summer.

Material studied Amador County: Thiers 32641. Sierra County: Thiers 21117, 32926, 32927.

Observations As the name indicates, the most striking characteristic of this fungus is the conspicuous amyloid reaction of the spores and the differential staining of the hyphal septations. Both amyloid reactions are typically strong enough to be seen clearly with the low-power objective of the microscope. It is interesting to note that a similar staining of the septa has been observed in Boletus calopus. In most other features this fungus is somewhat suggestive of G. turbinatus, although the flesh did not change to blue.

Edibility undetermined.

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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