E-Flora BC: Electronic Atlas of the Flora of British Columbia

Summary:
Features include 1) a somewhat spherical fruitbody with the base indented, 2) a surface that is white to olivaceous or brown but soon stained blue where bruised, 3) a spore mass that is white staining blue and becoming dark brown from spores, 4) an unbranched columella that extends through the spore mass, 5) underground growth under conifers, and 6) brown spores with even to irregular longitudinal ridges on 4-spored basidia. Kuo(12) provided evidence for the inclusion of Chamonixia caespitosa in Leccinum. Leccinum caespitosum was listed as a synonym of Chamonixia caespitosa in the online Species Fungorum accessed June 26, 2020. It is infrequent among false truffles in the Pacific Northwest (Trappe(13)).

It has been found in WA, OR, CA, NY, France, and Germany, (Castellano). It has been found from southwestern BC to northern CA, CO, (Trappe(13)). There is a Paul Kroeger collection from BC deposited at University of British Columbia.

Outer Surface:
0.5-2.6 x 0.8-4cm, somewhat spherical, the base indented; white or when well matured olivaceous, "quickly staining deep blue when exposed or cut"; felty; peridium readily separable, (Castellano), 2-3cm across, 1.3-2cm high, somewhat spherical to flattened on top, slightly lobed, depressed around a short stem; "white at first, slightly tinged buffish brown when the spores mature, rapidly turning deep indigo blue when bruised, this color eventually fading to greenish blue, but then remaining almost unchanged in drying"; peridium separable (when mature often peeling away in places), silky fibrillose, about 0.04cm thick when fresh, thinner in places, peridium absent or very little developed around stem, (Smith), 1.5-2(3)cm across, +/- spherical, "whitish at first, later brown, spotting black-blue when handled"; smooth to somewhat wrinkled, finely fibrillose to bald; peridium 0.03-0.05cm thick, (Breitenbach)

Stem:
stem-columella varying from percurrent [going through spore mass], 0.2-0.3cm thick and protruding from the base, to only a small basal pad, "the context at first white but later often becoming yellow to pale orange-brown near and below the base, quickly blueing when exposed", (Castellano), about 0.4cm high, 0.3cm wide, solid, "narrowed toward the base which continues into white rhizomorphs"; white, turning blue like the outer surface of the fruitbody; columella percurrent through the spore mass "as a narrow but distinct unbranched structure" about 0.05cm wide, (Smith), base tapering into short rudimentary stem, (Breitenbach), with a prominent basal rhizomorph (Trappe, M.)

Interior:
"with labyrinthine locules, nongelatinized", when young "white and staining blue when exposed, especially near peridium", when mature "dark brown from spores massed on the locule surfaces", (Castellano), "chambers small, oblong, not filled with spores at maturity", visible next to stem as peridium is absent or little developed around stem; "white at first, then dark army brown to vinaceous buff", (Smith), chambers irregularly oblong; spore mass white when young, brown-black when mature, (Breitenbach)

Odor:
pleasant, slightly resinous, (Castellano), not distinctive (Smith)

Taste:
not distinctive (Castellano, Smith)

Microscopic:
spores 13-22 x 10-16 microns excluding ornamentation, broadly elliptic, "6-14 straight to spiraling, often forked, dark brown, longitudinal ridges 3-5 microns tall, the lateral margins of the ridges ragged, the ridges not meeting at the spore apex", sterigmal attachment +/- 1 x 2 microns; basidia 4-spored, 32-38 x 15-20 microns; cystidia absent; trama of colorless, subparallel hyphae 3-5 microns wide, "the walls thin or slightly gelatinous thickened"; peridial subcutis of several tiers of more or less isodiametric, colorless, thin-walled cells up to 30 microns in diameter, often in radially aligned rows; peridial epicutis of loosely interwoven to appressed, colorless, thin-walled hyphae 7-9 microns wide; clamp connections absent, (Castellano), spores 18-20.5 x 12.7-15.2 microns, oblate, rich brown when mature, epispore long remaining colorless, finally brown, "irregularly wrinkled to form 8-10 longitudinal ribs", apex "slightly papillate but this often obscured by the wrinkles of the epispore", sterigmal appendage short, narrow, and colorless; basidia 4-spored, mostly about 36 x 18 microns, "in a true hymenium"; subhymenium "somewhat indefinite in thickness, of isodiametric cells"; hyphae of tramal plates 4-5 microns wide, colorless, only slightly gelatinous; "hypodermial zone of almost isodiametric cells somewhat radially arranged"; epicutis of peridium of appressed yellowish hyphae 7-9 microns wide; clamp connections absent, (Smith), spores 18-22 x 13-15 microns, oval, with longitudinal ribs, apex tuberculate, base with distinct apiculus; basidia 2-4-spored, 40-50 x 15-20 microns, clavate, (Breitenbach)