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).