Flora of North America species comparison

Species ca. 35 (6 in the flora).

The morphology of the inflorescence has received various interpretations. One suggested that the inner transparent scale represents five perianth members that correspond to the bristles subtending the achenes in some species of Scirpus (S. Friedland 1941). Another proposed that Lipocarpha is a highly reduced derivative of a Cyperus-like ancestor (J. Raynal 1967); that view was accepted by G. C. Tucker (1987) and P. Goetghebeur and A. Van den Borre (1989). The shared feature of Kranz anatomy of the “Cyperus type” further strengthens Raynal’s proposal. The achene and subtending scales of Lipocarpha are thus homologous to a single spikelet of Kyllinga or Cyperus. The interpretation of the secondary scales of Lipocarpha (Hemicarpha) as reduced scales of a spikelet (J. Raynal 1967) appears more plausible than the view of the secondary scale as fused perianth members (S. Friedland 1941).

Lipocarpha drummondii and L. aristulata have been frequently confused and misidentified as each other or as L. micrantha. Reports of those species, or their synonyms, should be confirmed by examining supporting specimens. Lipocarpha squarrosa (Linnaeus) Goetghebeur, a native of southern Asia, is known as an adventive from the Gulf Coast of Florida; it is not included in the species count. It has subtrigonous achenes and three stigmas, and it would seem to key to L. maculata in the following key; however, it is a smaller plant, at most 20 cm tall, with anthers only 0.15–0.2 mm and achenes 0.4–0.55 mm.

(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.)