Plants moderate-sized to robust; upright, prostrate, or aquatic; green, pale yellow, golden brown, dark brown, tinged with red in exposed sites and purplish in aquatic forms; capitulum rounded and often strongly twisted. Stems pale green to brown, darker in aquatic forms; superficial cortex of 1 layer of enlarged, thin-walled cells. Stem leaves lingulate to ovate-lingulate, 1.3-2 mm; apex truncate to rounded, usually denticulate; hyaline cells typically fibrillose for 1/2 of leaf or more, often 1-2-septate, convex surface with 4-12 or more pores per cell along the commissures, concave surface with fewer pores. Branches usually curving, often large and tumid. Branch fascicles with 2(rarely 3) spreading and 1-2(-3) pendent branches. Branch leaves broadly ovate to ovate-lanceolate, 1.3-2.5 mm, greatly elongated in aquatic forms, straight or infrequently subsecund or subsquarrose; hyaline cells with 10-22 pores along the commissures on the convex surface, no or fewer pores per cell (1-8) on the concave surface. Sexual condition dioicous. Capsule exserted, with few pseudostomata. Spores 27-34 µm; finely papillose on both surfaces, with distinct raised Y-mark sculpture (indistinctly bifurcated Y-mark) on the distal surface; proximal laesura less than 0.5 spore radius.
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