"Leucopaxillus albiformis"

[ Basidiomycetes > Agaricales > Tricholomataceae > Leucopaxillus . . . ]

by Michael Kuo

This is an easily recognized Leucopaxillus found on the West Coast under conifers. It shares the features that define the genus Leucopaxillus (gills that are separable as a layer, copious mycelium on the stem base, a white spore print, and spiny amyloid spores) and is quite sturdy; its white to pale tan cap can reach 30-40 cm across. Its most distinctive feature, however, is its roughened-scaly stem, which is usually swollen in the middle or near the base and has a pinched-off extension under the swollen area.

But while it is easily recognized, this mushroom is not so easily named. Its official taxonomic label at this point in time is Leucopaxillus albissimus var. paradoxus f. albiformis--rather a mouthful and, more importantly, probably inaccurate in several ways; see the discussion below if you care (or if you just want to see cool photos of 100-year-old mushrooms and mycologist's notes).

"Leucopaxillus albiformis" is probably not poisonous, but it is tough-fleshed, frequently bitter, easily confused with poisonous species of Clitocybe--and often smells bad. I do not recommend experimenting.

Description:

Ecology: Saprobic, decomposing the litter of conifers--especially that of Redwoods, cedars, and firs; growing scattered, gregariously, or in loose clusters; often found around--or even growing from--decaying stumps and logs; Pacific Northwest and northern California; fall and winter.

Cap: 5-40 cm; convex with an inrolled margin when young, becoming broadly convex or flat; dry; smooth or very finely velvety (like kid leather), sometimes becoming cracked with age; white (especially when young), buff, yellowish, or pale tan; the center usually darker than the margin with maturity; the margin often broadly lined.

Gills: Attached to the stem or running down it; close or crowded; separable from the cap as a layer; whitish to dirty yellowish when mature.

Stem: 5-20 cm long; up to 5 cm thick; rarely equal but usually substantially swollen in the middle or near the base, with a pinched-off projection extending below the swollen part; roughened-scaly; whitish, discoloring with age; basal mycelium often copious.

Flesh: White; thick; quite hard; not changing on exposure.

Odor and Taste: Odor not distinctive, fragrant, or foul (like coal tar or swamp gas); taste mild or bitter.

Spore Print: White.

Microscopic Features: Spores 5.5-8.5 x 3.5-6 µ (including ornamentation); more or less elliptical; spiny with amyloid warts. Cheilocystidia and pleurocystidia absent.

REFERENCES: (Murrill, 1913) Singer & Smith, 1943. (Murrill, 1913; Singer & Smith, 1943; Smith, Smith & Weber, 1979; Arora, 1986.)

Murrill (1913) described Clitocybe albiformis as a new species, apparently without collecting it himself, on the basis of two California collections made by James McMurphy. The description Murrill published in Mycologia can be found in the right-hand column. Though he designated McMurphy's 1903 collection as the type, he packaged it with a 1911 McMurphy collection; curators at the New York Botanical Garden Herbarium have identified which of the mushrooms in Murrill's box probably represent the 1903 type.

Though Murrill's published description calls the stem "slightly fibrillose below, finely tomentose above," his handwritten notes for the 1903 collection call the stem surface "slightly roughened with fibrillae." And while his published account calls for a "cylindric to ventricose" stem, his notes on the 1911 collection describe the stem as "tapering from a bulbous base" and include a drawing of a mushroom with a swollen base. His notes on the 1903 collection (linked above) call the stem "cylindrical," but the dried 1903 type specimen (photo) is clearly ventricose.

Singer & Smith (1943) studied Murrill's type collection and found its spores to measure 5.8-8 x 3.5-5 µ, despite the substantially smaller dimensions published by Murrill. They also discovered that the spores were covered with amyloid warts, placing the mushroom in Leucopaxillus. However, Singer & Smith felt that Murrill's species was actually merely a form of a variety of Leucopaxillus albissimus. The "variety" was var. paradoxus, which they felt should be separated from other varieties of Leucopaxillus albissimus on the basis of its mild taste, habitat under conifers, and non-smooth stem surface. The "form" was defined on the basis of the gills being "yellowish in dried specimens" (the gills of Leucopaxillus albissimus var. paradoxus f. typicus, by contrast, were "white or whitish in dried plants if properly prepared").

The plot thickens. Singer & Smith didn't just create the variety name paradoxus out of thin air; they re-combined the name of a European species, Leucopaxillus paradoxus, defining it as a variety of Leucopaxillus albissimus. Mycologists, including both Singer (1986) and Smith (1979) have since re-elevated Leucopaxillus paradoxus to species status--as a hardwood-loving taxon with an equal stem that features a merely "unpolished" (Smith, Smith & Weber, 1979) surface. European descriptions (Moser, 1983; Hansen & Knudsen, 1992) agree with this concept.

All of this leaves Murrill's mushroom with the ridiculous and misleading name Leucopaxillus albissimus var. paradoxus f. albiformis; it is officially a form of a variety that no longer exists. Perhaps it is merely an "ecotype" or "form" of Leucopaxillus albissimus, not even worthy of varietal status . . . or perhaps it should be "Leucopaxillus albiformis," morphologically distinct and, more importantly, separated by geography and ecology (especially the proximity to stumps and rotting logs).

Further Online Information:

Leucopaxillus albissimus at MykoWeb

Clitocybe albiformis sp. nov.

   Pileus thick, firm, convex, cespitose, 5-9 cm. broad; surface nearly smooth, dry, glabrous, white, slightly cremeous at the center, margin entire, concolorous, strongly inflexed on drying; context thick, white, with the odor and taste of the ordinary field mushroom; lamellae distinctly decurrent, rather broad and close, several times inserted, plane or arcuate; spores globose, smooth, hyaline, 2-3 µ; stipe cylindric to ventricose, tapering upward at times, white, solid, slightly fibrillose below, finely tomentose above, 9-16 cm. long, 1-2.5 cm. thick.
   Type collected in humus under redwoods near Searsville Lake, California, January 6, 1903, James McMurphy 3. This species strongly suggests Tricholoma album, hence the specific name selected for it.

W. A. Murrill, 1913

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Cite this page as:

Kuo, M. (2007, February). "Leucopaxillus albiformis." Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/leucopaxillus_albiformis.html