3. Rhynchospora corniculata (Lam.) A. Gray (horned rush)
Pl. 79 g, h; Map 301
var. interior Fernald
Plants forming clumps
or dense colonies, usually with rhizomes. Aerial stems 80–190 cm long,
stout, often somewhat bulbous-thickened at the base. Leaves basal and
alternate, the uppermost leaves somewhat reduced, the leaf blade 8–100 cm
long, (6–)8–20 mm wide, flat or somewhat folded longitudinally.
Inflorescences diffuse, with numerous loose clusters of 4–14 spikelets.
Spikelets 15–25 mm long, lanceolate in outline, attenuate at the tip,
with 1(2) of the florets fertile. Spikelet scales 4.5–7.5 mm long, ovate,
pointed, with a raised midvein, yellowish brown to orangish brown. Perianth
bristles usually 5(3–6), 2–4 mm long, much shorter than the main
body of the fruit, of unequal lengths and somewhat broadened at the base,
smooth or minutely pubescent with upwardly pointing barbs, sometimes shiny. Fruits
with the tubercle 13–20 mm long, narrowly triangular-attenuate, extending
past the spikelet tip, minutely pubescent with upwardly pointing hairs, the
main body 3.5–5.5 mm long, obovate in outline, flattened, the surface
smooth or faintly or minutely reticulate, brown. June–September.
Scattered mostly in the
southeastern quarter of the state, locally north to St. Louis and Audrain
Counties, most commonly in the Mississippi Lowlands (southeastern U.S. west to
Texas; Caribbean Islands). Mesic to swampy bottomland forests, and along spring
branches; also along ditches and canals.
The var. interior
has variously been segregated from var. corniculata based upon its
shorter and narrower main bodies of the fruits. Most Missouri materials appear
to fall into the range of variation ascribed to var. corniculata;
however, some populations exhibit a range of variation that encompasses both
extremes. The varieties therefore do not appear to merit taxonomic recognition.
See the treatment of R. macrostachya for further discussion on the
separation of this species from R. corniculata.
This robust species
often has large, diffuse inflorescences and often occurs in large, dense
colonies. Vegetative shoots usually are produced during the later half of the
growing season and can outnumber the fertile stems.