RICCIA, in botany: A genus of the natural order of algae, belonging to the cryptogamia class of plants. There is no calyx, but a vesicular cavity within the substance of the leaf. There is no corolla; the antheræ are cylindrical, and sessile, placed on the germin, which is turbinated; the style is filiform, perforating the an-
thera; and the feed-case is spherical, crowned with the withered anthera; the feeds are hemispherical and pedicellated.