Plants perennial, often mat-forming, never stoloniferous or proliferating from spikelets. Rhizomes horizontal and long, or ascending and caudexlike. Culms 0.3–5 mm wide; distal leaf sheaths usually persistent, rarely disintegrating, papery to membranous, apex subtruncate to sometimes acute, tooth sometimes present. Spikelets: floral scales membranous to thinly papery; proximal scales empty. Flowers: styles 2-fid to 3-fid. Achenes yellow, orange, brown or greenish, biconvex, trigonous, or sometimes nearly terete, smooth at 30X, or rugulose or cancellate or reticulate at 10–30X. Tubercles distinct from achene summit in texture and/or color and form.

Species ca. 70 (22 in the flora): worldwide.

Eleocharis subg. Eleocharis ser. Eleocharis has been called by the invalid names Eleocharis ser. Palustriformes Svenson and E. sect. Palustriformes Zinserling. Species 1–7 belong to subser. Eleocharis (= E. ser. Palustriformes subser. Palustres Svenson, name invalid), which comprise the extremely difficult “E. palustris complex” (M. L. Fernald and A. E. Brackett 1929; L. J. Harms 1968; S.-O. Strandhede 1966; H. K. Svenson 1947); see 1. E. palustris for a discussion of this complex. Species 8–22 belong to subser. Truncatae Svenson, within which species 16–21 comprise the extremely difficult “E. tenuis complex” (L. J. Harms 1972); see 17. E. compressa for a discussion of this complex.

SELECTED REFERENCES

Fernald, M. L. and A. E. Brackett. 1929. The representatives of Eleocharis palustris in North America. Rhodora 31: 57–77. Harms, L. J. 1968. Cytotaxonomic studies in Eleocharis subser. Palustres: Central United States taxa. Amer. J. Bot. 55: 966–974. Harms, L. J. 1972. Cytotaxonomy of the Eleocharis tenuis complex. Amer. J. Bot. 59: 483–487. Strandhede, S.-O. 1965. Chromosome studies in Eleocharis subser. Palustres. III. Observations on western European taxa. Opera Bot. 9(2): 1–86. Strandhede, S.-O. 1966. Morphologic variation and taxonomy in European Eleocharis subser. Palustres. Opera Bot. 10(2): 1–187. Strandhede, S.-O. 1967. Eleocharis subser. Eleocharis in North America: Taxonomical comments and chromosome numbers. Bot. Not. 120: 355–368. Svenson, H. K. 1947. The group of Eleocharis palustris in North America. Rhodora 49: 61–67.