Flora of North America species comparison

The circumboreal Carex aquatilis var. aquatilis is very common in wetlands of the northern and montane portions of North America. The plants are usually rhizomatous; in very wet or flooded sites they may form cespitose clumps.

Carex aquatilis var. aquatilis is distinguished from the sympatric Carex stricta by the sheaths not ladder-fibrillose, obovoid and veinless perigynia that are rounded at apex, glossy achenes, and amphistomic leaves. It is often confused with C. emoryi, and distinguished by perigynia that lack veins, concave sheath apex, glossy achenes, and amphistomic leaves. In western North America, it is often sympatric with C. scopulorum and may be distinguished by the pale brown perigynia, glossy achenes, and amphistomic leaves.

Carex aquatilis and C. scopulorum occasionally hybridize; hybrids have been named as C. ×sphacelata T. Holm and C. ×chionophila T. Holm. Carex aquatilis var. aquatilis overlaps and may intergrade with C. aquatilis var. dives along the Pacific Coast, with var. minor along the Arctic coast, and with var. substricta in the Great Lakes-New England region. Much of var. aquatilis in the southern part of its range has been called var. altior (L. H. Bailey) Rydberg. The type for var. altior is a specimen of C. emoryi.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Genera ca. 100, species ca. 5000 (27 genera, 843 species in the flora).

No consensus exists regarding the number of genera and the overall relationships of genera within Cyperaceae. The most recent account of the family (P. Goetghebeur 1998) recognized 104 genera distributed among 4 subfamilies and 14 tribes. That arrangement differs somewhat from that of J. Bruhl (1995). With one minor exception the arrangement of the family here follows that of Goetghebeur.

The family is characterized by the occurrence of a number of unusual cytological features including: (1) chromosomes with diffuse centromeres, (2) post-reductional meiosis, and (3) pollen grains formed from tetrads in which 3 of the 4 microspores fail to develop. The first two features are found in at least some Juncaceae and are unique to the two families. Juncaceae also have pollen in tetrads, but in that family all four microspores produce pollen grains. Some species in some genera of Cyperaceae (particularly Eleocharis) possess chromosomes with localized centromeres (S. S. Bir et al. 1993). The wide range of chromosome numbers found in Cyperaceae is largely because of agmatoploidy; polyploidy has been hypothesized for some genera, especially Eleocharis, although polyploidy has not been demonstrated unequivocally.

Because of morphologic similarities in vegetative and inflorescence characters, the family has commonly been associated with Poaceae. Cytological features discussed above clearly indicate that to be a superficial similarity. Data from rbcL studies also support the view that Cyperaceae and Poaceae are not closely related (M. R. Duvall et al. 1993b; G. M. Plunkett et al. 1995); they do support the concept of close relationship between Cyperaceae and Juncaceae.

For most families of flowering plants the phenological data given are flowering times. Because most Cyperaceae cannot be reliably identified when in flower, in this volume fruiting time is given for all species by season, sometimes qualified by early, mid, or late, or by months. The fruiting time has been interpreted broadly to include the period when the fruit is more or less fully formed but not yet ripe. The fruiting period provided covers the entire range of the taxon. Quite a difference between fruiting periods in different parts of the range of the species may well occur, especially for widespread species and species with extensive elevation range.

For a recent, comprehensive review of the economic importance of Cyperaceae, see D. A. Simpson and C. A. Inglis (2001).

(Discussion copyrighted by Flora of North America; reprinted with permission.)