Trithuria filamentosa Rodway

Densely tufted, aquatic or subaquatic, monoecious perennial with short rhizome, usually green. Leaves numerous, erect, filiform, terete, 1-3 cm long, with persistent scarious bases. Scapes subequal to leaves; male capitula fewer than female; bracts 2-4, lanceolate, loosely sheathing, 3-5 mm long. Male flowers 4-6 per capitulum; stamens exserted sequentially; anther linear-oblong, to 2 mm long, red-purple; filament c. 6 mm long. Female flowers 8-20 per capitulum, crowded, red; pedicel to 0.8 mm long; ovary ovoid, c. 0.4 mm long; stigmatic hairs 5 or 6, subequal, 3-5 mm long. Fruit ovoid, smooth or wrinkled, obscurely 2-or 3-veined, c. 0.5 mm long, greenish-brown.

Grows in shallows of alpine lakes and streams and in mud at their margins.