On moss-covered trunks of deciduous trees. Autumn to early winter. Widespread, but rare in western lowlands, and not yet accepted from the UK. It is a rather common species in South Norway, especially on Acer platanoides and Fraxinus excelsior, but regarded as NT in the Norwegian Red List. Not recorded in the northern part of the country.

Pileus 2-10 mm across, hemispherical to convex or applanate with somewhat expanded margin, mostly with a depressed centre, but also with a small papilla, pruinose, glabrescent, sulcate, translucent-striate (disappearing when drying), at first white or beige, sometimes with a yellowish tinge in the centre, with age turning more brownish, dirty white, whitish-brown or pale brown with darker centre. Lamellae (6-)9-12 reaching the stipe, broad, arcuate to subhorizontal, the edge concave, broadly adnate, more or less decurrent, whitish. Stipe up to 12 mm long, more or less curved, equal or somewhat tapering downwards, minutely puberulous, towards the base often hirsute, whitish, with age turning brown from the base; the base covered with coarse, white fibrils. Odour none.

Basidia 23-27 x 7-9 µm, clavate, 4-spored and clamped, or 2-spored and clampless. Spores (7-)8-9(-11) x 6.5-8(-9.2) µm, Q = 1.0-1.2, Qav = 1.1, globose, smooth, non-amyloid. Cheilocystidia 17-34 x 5-10 µm, clavate to subcylindrical, clamped or clampless, somewhat curved to flexuous, apically broadly rounded. Pleurocystidia absent. Lamellar trama not vinescent in Melzer's reagent. Hyphae of the pileipellis 2.5-4.5 µm wide, clamped or clampless, smooth for the greater part, terminally covered with scattered, coarse, inflated, simple or broadly lobed excrescences 4.5-13.5 x 3-5 µm. Hyphae of the cortical layer of the stipe 2-3 µm wide, smooth, clamped or clampless, terminal cells (caulocystidia) clavate to irregularly shaped, clamped, smooth to very coarsely diverticulate or lobed.

According to Maas Geesteranus (1992: 461), Phloeomana alba can be 4-spored and clamped, but to my experience it more often appears to be 2-spored and clampless. This is in accordance with Robich (2003: 363).

Phloeomana alba may be confused with P. hiemalis (Osbeck) Redhead. The point is that not-quite-mature spores of P. hiemalis are just as globose as the mature ones of P. alba and of the same size. Also, it is not always easy to determine whether the lamellar edge in a young fungus is going to develop a convex outline (P. hiemalis) or a straight to concave one (P. alba). Maas Geesteranus (1992: 461) payed attention to these facts and provided some more distinguishing features.

Phloeomana hiemalis:

Phloeomana alba: