Summary:
The outstanding features are "the sparse development of the spines and the broad, spineless, fimbriate margin" (Martin). Features include 1) growth on dead wood of black cottonwood, 2) a brown, waxy fruitbody with spines sparsely and irregularly distributed, that fades to buff or pallid near the margin, the margin broad and fringed, without spines, 3) spores that are cylindric to allantoid, usually with numerous small droplets, germinating by repetition, 4) basidia that become cruciate-septate, 5) dendrophyses. The description is derived from Martin. Roberts(3) says, "Based on the type description and illustrations, this Canadian taxon is clearly unrelated to Protodontia, having an effused brown basidiome with fimbriate margin, non-myxarioid basidia, and comparatively large allantoid spores. It would appear to be referable to the genus Heterochaete" (genus names italicized).
Protodontia oligacantha was described from BC. It is known only from the type and three paratype specimens (Ginns).
Fruiting body:
broadly effused [spread out], up to 1.3cm by 0.5cm in extent, possibly larger, waxy when moist, the spore-bearing surface drying horny; "benzo brown" to "cinnamon drab", fading to buff or pallid near the margin; margin broad, thin, fimbriate [fringed], white (no suggestion that margin is ever determinate); spines sparsely and irregularly distributed, (where most abundant, 3-5 per square millimeter), blunt, broad, somewhat fimbriate, white, up to 0.06cm long and 0.035cm across at base, tapering toward tips
Microscopic:
SPORES (9)10-12(13) x (4)4.5-5(5.5) microns, cylindric to allantoid, usually with numerous small droplets, sometimes with 1-3 large droplets and numerous smaller ones, germinating by repetition; PROBASIDIA spherical to ovate or pyriform, "mostly 13-20 x 9-12 microns, becoming cruciate-septate, each cell producing a thick, rather short epibasidium, 2-2.5(3) microns in diameter"; DENDROPHYSES "3-4 microns in diameter at base, branching subdichotomously several times and irregularly attenuated toward the tips, sometimes with clamp-connections"; spines "fertile over most of the surface, as is the hymenium between them, but the extreme tip is often sterile", "owing to protrusion of an extension of the intermediate yellow layer, giving them a fimbriate appearance when examined dry under a binocular", spines "tend to be borne in lines on whitish strands, which makes the hymenial surface appear faintly reticulate under a lens"; hymenium "composed of colorless basidia and dendrophyses", the latter rather difficult to see since the terminal part does not stain; "in section 65-230 microns thick between the spines, composed of a colorless hymenial layer 20-40 microns thick, a yellowish basal layer of horizontal hyphae and an intermediate layer of variable thickness, clear yellow by transmitted light, which penetrates the spines, composed of indistinct agglutinated hyphae intermingled with crystalline accretions"
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