Public Note:
Fruit bodies up to 60 x 4 mm, simple clubs, solitary to cespitose in groups of 2-3, arising from a small, whitish mycelial patch. Stipe equal, pallid at base ("tilleul buff") grey above ("pale neutral-grey"), appearing silky. Club matte on surface, equal, often somewhat wrinkled or subsulcate, grey to bluish grey ["neutral-grey", "7 grey" "deep dull grey", "deep plumbeus", "mouse-grey"]; flesh more deeply coloured than hymenium outward, paler and more fibrous or stuffed within. Apex rounded. Taste and odour negligible. Macrochemical reaction: FCL = negative. Tramal hyphae of club 3-20 um diam., hyaline, undamped, thin-walled, strictly parallel, covered with small patches of amorphous material, and with occasional crystals. Subhymenium extensive, pseudoparenchymatous. Hymenium thickening; basidia 70-80 x 10-13 um, broadly clavate, bifurcate or clamped at base, more or less persistent after spore discharge; contents granular to multiguttulate at maturity; sterigmata (2-3)-4, stout, arising as rounded lobes, eventually up to 10 urn long, curved-ascending. Spores 9.4-11.2 x 7.9-9.0 um (Em = 1.08-1.41; Lw = 1.21; Lm = 10.3 um), broadly ellipsoid, conspicuously roughened; contents multiguttulate to uniguttulate; hilar appendix broad, papillate; ornamentation of narrowly truncate-conical spines up to 1.5 um long.COMMENTARY: Again, spore ornamentation provides a most confusing situation. Clavaria ardosiaca not only shares almost identical fruit bodies (colour, stature, etc.) but unusually large spores, however, its spores are smooth. At the same time, C. musculospinosa specimens vary greatly in this character, for TENN no. 43541 and Horak's collections show almost no smooth spores, whereas TENN no. 43540 shows very few ornamented spores. Were the rough spores not seen on TENN no. 43541, it would surely have been accessioned under C. ardosiaca. Thus, although it would appear that species pairs exist - one with ornamented spores, the other with smooth - this may be artifactual, really representing a cline under unknown controls. The wide, long basidia are a reflection of the large spores. Sterigmata number is very variable, perhaps (as in many other taxa) related to the unusual variation in spore dimensions and E values. Sterigmata are blunt until near maturity.
[JAC] The presence of spiny spores in the type collection of C. ardosiaca on recent examination blurs the distinction between this and C. ardosiaca. This material is poor, and has few spores. My section had a few more spiny spores than C. ardosiaca but mostly smooth, length=9.6–13.1µm (µ=11.3, σ=0.92), width=6.2–9.3µm (µ=7.7, σ=0.83), Q=1.2–1.7µm (µ=1.48, σ=0.14), n=15. Recent phylogenetic work indicates that spines are not a good character, and, it seems, neither is spores size. Thus I believe this and C. ardosiaca are synonyms and the name C. ardosiaca seems preferable.
J.A. Cooper, Nov. 2017