The Mosses which constitute this family are of a brownish-black
colour and are found living on rocks. The sporangium resembles
that of the Liverworts inasmuch as it opens by four valves, but
these continue attached to each other at the apex as well as at
the base (Fig. 193).--There is only one genus: _Andreæa_.
=B.= The stalk is formed from the lower portion of the
sporogonium. The columella is continued to the summit of the
sporangium and united with it (_Archidium_ has no columella.)