They are small, delicate acrocarpous mosses (meaning that the capsules are formed at the tips of vertical branches) that form dark brown or reddish cushions on wet siliceous rocks in mountainous areas. The capsule lacks theperistome teeth and operculum of other mosses, and opens by splitting along 4 vertical slits, the four valves remaining joined at the base and apex. The capsule of Andreaea has no seta, but the sporophyte (Spf in the diagram below) instead is supported by apseudopodium (ps) derived from gametophytetissue, as in Sphagnum and the columella is enclosed within the sporangium. The spores germinate to give thalloidprotonemata.
(From Wikipedia, February 2015)