8a2b. ELEOCHARIS R. Brown (subg. ELEOCHARIS sect. ELEOGENUS) ser. OVATAE Svenson, Rhodora. 31: 128. 1929.
Plants annual (rarely perennial?), densely tufted, rhizomes absent. Leaves: distal leaf sheaths persistent, proximally stramineous (to reddish), distally stramineous or green with a tooth usually present on some or all culms. Culms with their spikelets usually fruiting simultaneously, long to very short in one plant, terete. Spikelets: basal spikelets absent; proximal scale without (sometimes with) flower, usually clasping less than all of culm;. Achenes stramineous ripening to dark brown, biconvex or to 1/3 of achenes greatly compressed-trigonous, lateral angles usually prominent (especially distally), smooth, apex not constricted proximal to the tubercle. Tubercles sessile on achene summit, dorsiventrally greatly compressed, proportionally much thinner than achene in cross section.
Species 6 (6 in the flora): temperate North America and Eurasia.
The delineation of the species of ser. Ovatae needs further study (H. K. Svenson 1957). Although some authors have combined two or more of the six species of ser. Ovatae herein recognized, the studies by D. M. Hines (1975), B. M. H. Larson and P. M. Catling (1996), and A. Haines (2001) indicate that they should be treated as distinct species. The species are separable mainly on the basis of tubercle dimensions and perianth bristle characters. Stamen and stigma numbers are difficult to observe and are more variable within species and in the same plant than given in the literature. Stamens are often caducous, and the filaments are often not easily distinguished from the bristles, on which the spinules are mostly appressed and often not clearly evident. The anthers are often poorly developed and lack evident pollen. In most species the styles are often trifid in the distal parts of the spikelets and bifid in the proximal parts. The tubercles are often bent toward the spikelet axis, and when the perianth bristles exceed the achene their distal parts are also bent adaxially. Although usually clearly annuals without rhizomes, where winters are mild, plants sometimes have ascending rhizome-like caudices, and it seems possible that some plants may survive the winter. The distributions of the species herein are based on D. M. Hines (1975), B. M. H. Larson and P. M. Catling (1996), A. Haines (2001), and herbarium observations.
Haines, A. 2001. Eleocharis aestuum (Cyperaceae), a new tidal river shore spikesedge of the Eastern United States. Novon 11: 45–49.