Summary:
Also included in Corals category. Cotylidia diaphana has 1) a whitish to pale brown, translucent fruitbody which is vase-shaped or funnel-shaped or split into petal-like lobes, with radiating silky fibrils on the upper surface, 2) the undersurface smooth but under a hand-lens bristly, 3) slender smooth stem, 4) growth on the ground, 5) whitish spore deposit, and 6) cystidia on the lower (spore-bearing) surface. Molecular work places Cotylidia in the Rickenella clade that falls either in Hymenochaetales or Agaricales.

Microscopic:
spores 4-6(8) x 2.5-4 microns, elliptic, smooth; long narrow projecting cystidia present, (Arora), spores 4-6 x 2.5-4 microns, elliptic to oval, smooth, colorless; cystidia 69-100 x 9.5-13 microns, colorless, hair-like, thicker than basidia and projecting beyond them, (Lincoff), spores 4-6(7) x (2)2.75-3.5 microns, elliptic, thin-walled, colorless, with a distinct, oblique apiculus; basidia 4-spored, up to 28.6 microns long and 5-6 microns wide, clavate or subcylindric; cystidia up to 130 microns long and 8-15 microns wide, long cylindric or slightly clavate, thin-walled, originating in the trama just above the hymenium, may project up to 80 microns beyond the basidia, may become 1-septate; hymenium thickening, reaching 78 microns thick at a point 0.5cm from the margin of the fruitbody; hyphal structure monomitic, consisting of generative hyphae 2-6(7) microns wide, colorless, branched, walls thin or distinctly thickened, clamp connections absent, (Reid(6))

Spore Deposit:
whitish (Arora)

Notes:
The distribution includes WA, PQ, AL, CA, IA, IL, IN, MI, MN, MO, NY, OH, PA, UT, and WV, (Ginns), and MS (Lincoff). It is also reported from Argentina, Brazil, Jamaica, and China, (Reid). There is one collection from BC with this label at the Pacific Forestry Centre determined by J. Hanson.

Synonyms and Alternate Names:
Hyphodontia breviseta (P. Karst.) J. Erikss. Symb.
Kneiffia breviseta P. Karst.
Polyporus albellus Peck
Polyporus chioneus Fr.