The name refers to the ephemeral habit of these mosses.

Dioicous or rhizautoicous. Plants 0.5–2.5 mm tall, acaulescent or almost so, with a conspicuous protonema. Leaves 2–12, the outer bract-like, oval to narrowly lanceolate, the inner perichaetial leaves linear, lanceolate, spathulate or ligulate, acute to finely acuminate; costa absent, rudimentary or more well developed, sometimes excurrent in an awn, usually absent towards the leaf basal.

Perigonia gemma-like, on rhizoids, often with associated the protonema. Calyptra campanulate, papillose or smooth, with 1–4 splits at the base, sometimes cucullate; vaginula subglobose, rarely ellipsoidal. Capsules cleistocarpous, ±globose, rarely ellipsoidal; stomata present at base. Spores usually papillose.

The protonema is often more conspicuous than the gametophores, and the vegetative leaves are usually much smaller than the perichaetial leaves. While the latter is the most useful diagnostic feature, perichaetial leaves do not enlarge until after fertilisation. As a result, immature plants can be difficult to determine. The calyptra cells can be tumid at first, but they later collapse and appear ±smooth.

A genus of about 30 species which is widely distributed in temperate regions of both hemispheres. Represented in Australia by six species, two of which are endemic.

Ephemerum Hampe, Flora 20: 285 (1837), nom. cons.. Lectotype: E. serratum (Hedw.) Hampe

Ephemerum whiteleggei Broth. & Geh., Oefvers. Förh. Finska Vetensk.-Soc. 37: 156 (1895).Type: North Shore and Balls Head Bay, Sydney, N.S.W., T.Whitelegge 45 & 221; syn: H-BR, MEL, NSW.

This is Eccremidium minutum (Mitt.) I.G.Stone & G.A.M.Scott (Ditrichaceae).

Stone, I.G. (1996). A revision of Ephemeraceae in Australia. Journal of Bryology 19: 279–295.

Stone, I.G. (2012). Australian Mosses Online 41. Ephemeraceae. Australian Biological Resources Study, Canberra. Version 9 June 2012. http://www.anbg.gov.au/abrs/Mosses_online/41_Ephemeraceae.html

First published as: Stone, I.G. (2006). Ephemeraceae, in McCarthy, P.M. (ed.) Flora of Australia 51: 163–167. (Australian Biological Resources Study, Canberra & CSIRO Publishing, Melbourne.)