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Cyperaceae

Lipocarpha R.Br.

Kingdom: Plantae Rank: Genus Parent: Cyperaceae Status: Valid

Common Names:

  • HALFCHAFF SEDGE - English, United States of America

Morphological Description

Diagnosis: Tufted, delicate, glabrous annuals 1–15(–20) cm tall; leaves basal, 2, one without blade; ligules absent; inflorescence of 1–3 ovoid, sessile, spikelet-like spikes 1–5(–8) mm long, the spikes of numerous single-flowered spikelets whose scales (here called floral scales in contrast to the included hyaline scales) are spirally and imbricately arranged to make the whole spike appear like a single spikelet; in ours inside each floral scale there is 1 inconspicuous hyaline scale or bracteole often split and torn by or adhering to the achene; floral scales with 2–3 prominent veins (often with two more conspicuous medial veins and a less conspicuous central vein); inflorescence subtended by 1–3 bracts, 1 of these much larger and appearing like a continuation of the culm, the inflorescence thus appearing lateral; stamen 1; stigmas 2; achenes narrowly obovoid to obovoid, terete, 0.4–0.8 mm long, granular, very minutely apiculate, without a tubercle.

Other

Notes: A genus of ca. 35 species, pantropical and in some wet warm temperate regions (Tucker 2002b). The inflorescences and flowers are much reduced. Recent molecular studies (e.g., Muasya et al. 2002) suggest that it is embedded within a paraphyletic Cyperus. The species treated here as Lipocarpha have historically been segregated into the genus Hemicarpha (e.g., Friedland 1941), but according to a number of authors (e.g., Haines & Lye 1971; Tucker 1987, 2002b), the two extremely similar groups are more appropriately merged. However, Kral (2001) disagrees and maintains them as separate genera. According to Friedland’s (1941) range map, three difficult to distinguish taxa occur in East TX. He recognized these as varieties of Hemicarpa micrantha and said that in order to key them, “… the spikelet must be boiled and then dissected under a binocular dissecting scope capable of at least a magnification of forty diameters.” Tucker (1987, 2002b) and Kartesz (1994, 1999) recognized these taxa as species (Lipocarpha aristulata (Coville) G.C. Tucker, L. drummondii (Nees) G.C. Tucker, and L. micrantha (Vahl) G.C. Tucker). Using the key from Friedland (1941), we were completely unable to consistently distinguish the taxa; the following detailed key was developed by S.D. Jones using TX material. All three species are essentially identical vegetatively; reproductive material is thus essential for identification to species. The inconspicuous hyaline scale or bracteole inside each floral scale is not homologous to the scales or bristles of other members of the Cyperaceae (e.g., Scirpus). Rather, each “floret” of the “spikelet” is actually a highly reduced 1- flowered spikelet similar to those in Kyllinga. The hyaline scales are thus homologous to the sterile scales found in the spikelets of Kyllinga (Koyama 1982; Hooper 1986; Tucker 1987, 2002b; Goetghebeur & Van den Borre 1989; Yatskievych 1999). Therefore, while Lipocarpha superficially appears closer to such taxa as Fimbristylis or Scirpus, its actual relationships are with such genera as Kyllinga and Cyperus (Bruhl 1995; Yatskievych 1999). All three East TX species are inconspicuous and rather rarely collected. (Greek: lipo, to fall, and carpha, chaff, in reference to the deciduous transparent second scale of the spikelet in many species—Tucker 2002b)