Scirpus lacustris var. carinatus sensu C.B. Clarke in Hook.f., Fl. Br. Ind. 6: 658. 1893; ? S. triquetriformis V. Krecz., in Ovcz., Fl. Tadjiksk. SSR 423 (1963).

Perennial, 50-60 cm. Stem 3-6 mm diam., trigonous above, terete or obtusely trigonous below, glaucous green. Inflorescence multiple spike or anthelodium, 35-65 mm; lowest bract 10-30 mm; primary branches up to 40 mm; tubular prophyll wide, light brown; secondary multiple spikes with 3-7 spikes; secondary branches to c. 10 mm. Spikes mostly solitary or geminate, 5-10 x 2-4 mm; glumes 2.5-3.5 mm, mucro to 0.8 mm, with or without reddish barbs, sides brown, smooth, sometimes red dotted. Perianth bristles 5-6, equalling nut or longer; stigmas 2. Nut 2-2.1 x 1.3-1.5 mm.

Fl. Per.: July - August.

Rice fields; standing water; Distribution: From Afghanistan to Kashmir; northwards probably to Kazakhstan.

Schoenoplectus lacustris with its subspecies is known in Europe to hybridize with S. triqueter (see e.g. Schultze-Motel, in Hegi, Fl. Mitteleuropa, 2(1): 41-42, 1967). The hybrid described above is glaucous green and pistils have two stigmas. This suggests that subsp. hippolyti, probably commonest in area, is involved. Assumed hybrid is apparently fully fertile. Raymond (Dan. Biol. Skr. 1965) and Stewart (l.c. 1972) cite the Aitchison specimens under S. lacustris var. luxurians (Miq.) Raymond.