VicFlora: Solenostoma orbiculatum

Mats on soil or rocks, bright green to yellowish or brownish green, dioicous. Stems prostrate to ascending; branches emerging from stem laterally near unmodified leaves. Leaves orbicular, 1000–1750 mm long, 1375–2500 μm wide, succubous, arching outwards away from stem, imbricate, decurrent, unistratose, deeply concave adaxially, with plane or recurved margins, with rounded or weakly emarginate apices. Leaf cells in centre toward base oblong, to 80 µm long and 43 µm wide, striolate-papillose, thin-walled, with small distinct trigones, oblong, rounded-quadrate or elliptic and firm-walled toward margins and apex and 28–53 µm long and 25–40 µm wide, with (2–) 3–6 oil bodies; oil bodies pale grey, finely granular. Rhizoids common along ventral stem and bases of leaves. Androecia terminal, rarely becoming intercalary, with 3–8 pairs of leaf-like bracts, each with 2–3 antheridia. Female bracts broadly reniform, weakly fused with base of perianth; bracteoles absent. Perianth ellipsoid, plicate in apical half, emergent for half of length from bracts, crenulate and beaked at mouth. Capsule short-ellipsoid, 2–3-stratose; spores finely papillose.

GGr, VAlp. Recorded from fast-flowing creeks along the Great Dividing Range. Also, Queensland, New South Wales, Australian Capital Territory, Tasmania and New Zealand.

Very similar to S. inundatum, but has wider cells and the leaves seem to be always orbicular. The habitat of the two species also differs with S. inundatum mostly occurring on embankments of tracks and in seepages, whereas S. orbiculatum occurs in fast-flowing streams. Hepatostonophora paucistipula and Syzygiella sonderi are other unlobed, superficially similar species of fast-flowing streams that can be confused with S. orbiculatum. Hepatostonophora paucistipula has small bifid or triangular underleaves that are easily overlooked, whereas there are no underleaves in Solenostoma. Syzygiella sonderi has bracteoles below the perianth, however, both S. sonderi and S. orbiculatum are rarely fertile in Victoria. Syzygiella sonderi has branches that emerge from the ventral side of the stem, whereas they are strictly lateral in origin in S. orbiculatum. The leaves of the two species also differ when dry. In S. orbiculatum the leaves, when dry, remain spreading perpendicular to the stem and the apices often tend to recurve, and can also become wrinkled and slightly contorted. In S. sonderi the leaves do not become contorted and the leaves fold inwards to be pressed against the surrounding and their opposing leaves.