11. Lipocarpha R. Br.

(Goetghebeur and Van den Borre, 1989)

Plants annual (perennial elsewhere), tufted, glabrous. Aerial stems few to many per plant, 2–10(–15) cm long, 0.3–0.5 mm in diameter, erect to spreading, unbranched, not ribbed. Leaves basal, 1 per aerial stem, usually also with an additional bladeless sheath below the leaf, the sheath short and without a ligule, the leaf blade 1–10 cm long, 0.3–0.5 mm wide, spreading to ascending, the margins mostly flat. Inflorescences terminal but appearing lateral, subtended by 2–3 leaflike bracts, the longest of these erect or nearly so, stemlike, the others usually spreading to reflexed, composed of 1–3(–4) spikelets, these sessile in headlike clusters. Spikelets 2–6 mm long, ovate in outline. Florets many per spikelet, several-ranked in an overlapping spiral pattern, perfect. “Perianth” (see discussion below) of 1–2 small, papery scales, sometimes reduced or rarely absent. Stamen 1(2). Styles not or minutely expanded at the base, not persisting on the fruit as a tubercle . Stigmas 2 (3 elsewhere). Ovaries and fruits naked, without a perigynium (saclike covering). Fruits 0.5–0.8 mm long, narrowly obovate to nearly elliptic in outline, broadly elliptic to nearly circular in cross-section, sometimes somewhat flattened on 1 side, the surface brown to dark brown, less commonly gray to black, often somewhat iridescent, sometimes bluish gray–glaucous, minutely pebbled in numerous vertical ranks. About 35 species, North America to South America, Caribbean Islands, Africa, Madagascar, Asia, south to Australia.

As defined here, Lipocarpha includes species sometimes segregated in the genus Hemicarpha Nees ex Arn. The two groups are said to differ in the number of small scales (in addition to the larger scale subtending each floret) subtending the ovary and fruit (2 in Lipocarpha sensu stricto vs. 0–1 in Hemicarpha). However, Goetghebeur and Van den Borre’s (1989) monograph of the complex indicated that this character cannot be applied consistently for all species. Recently, Bruhl’s (1995) phylogenetic studies have suggested that more detailed taxonomic research into this problem may lead to the reestablishment of Hemicarpha, based on a different set of morphological characters. The segregate Hemicarpha applies to a group of 6–8 species occurring mostly from North America to South America, but also in Africa.

The three species of Lipocarpha in Missouri are very similar in general appearance. They are virtually identical vegetatively and can be differentiated only on the basis of details of spikelet morphology (Lawson, 1973). The “perianth” scales in the genus are apparently not homologous to the scales or bristles found in other genera of Cyperaceae, such as Fuirena and Scirpus. Instead, each floret of the spikelet actually represents a reduced 1-flowered spikelet, as is found in Kyllinga, and the “perianth” scales are homologous to the sterile scales of the spikelets in that genus (Tucker, 1987; Goetghebeur and Van den Borre, 1989). Thus, although Lipocarpha appears morphologically similar to some species of Fimbristylis or Scirpus, it is actually more closely related to Kyllinga and other members of the Cyperus alliance (Bruhl, 1995).