keys to the vascular plants of east texas - Botanical Research ...

600 CYPERACEAE/ELEOCHARIS
Eleocharis obtusa (Willd.) Schult., (obtuse, blunt), BLUNT SPIKE-RUSH. Tufted annual 3–50 cm
tall; distal leaf sheath apex angled to a short broad point with a minute tooth 0.3 mm or less
long; spikelets ca. 3–12 mm long, usually broadly ovoid to oblong-ovoid, obtuse, usually with
(15–)50–150 scales; stamens usually 3; styles usually both 2-fid and 3-fid in same spikelet; achenes
mostly biconvex, 0.8–1.2(–1.5) mm long, pale to dark brown; tubercle 0.35–0.5 mm long, nearly as
wide as summit of achene. Moist sandy soils, pond margins; widespread in East TX; also e Cross
Timbers and Prairies, e Edwards Plateau, and Ochiltree Co. (Turner et al. 2003) in the Panhandle; s
Canada and widespread in the U.S., more commonly in the e 1/2 of the country. Late Apr–Oct. [E.
ovata (Roth) Roem. & Schult. var. obtusa (Willd.) Kük., Scirpus obtusus Willd.] Yatskievych (1999),
following Gleason and Cronquist (1991), submerged this species and E. engelmannii into E. ovata
(Roth) Roem. & Schult. (the oldest valid name for the complex), thus recognizing the taxonomically
confusing E. ovata complex as a single species. He indicated that in Missouri he had been
unable to find consistent differences between the three species. However, we are following Larson
and Catling (1996) and the recent treatment in Flora of North America (Smith 2002d) in recognizing
E. obtusa as a distinct species. Smith (2002d) noted that E. ovata “consistently differs in its
mostly 2-fid styles, mostly two stamens, and especially its narrower tubercles [1/2–3/4 as wide as
achene].” Intermediates with E. engelmannii also are known (Smith et al. 2002).
Eleocharis occulta S.G. Sm., (hidden, in reference to the rhizomes being concealed by the culm
bases). Tufted rhizomatous perennial; culms 56 cm or less tall; distal leaf sheath apex truncate
or nearly so; spikelets 3–10 mm long, ovoid, with 20–50 scales; scales with long-pointed scarious
tips, all including the lowermost 2-fid apically; achenes obscurely trigonous, 0.7–1 mm
long, medium to dark brown; tubercles tiny, 0.15 mm or less long. Seeps and other wet areas, often
on calcareous soils; scattered in East TX, more commonly on w margin of area; also Cross
Timbers and Prairies and e Edwards Plateau; endemic to OK and TX. Mar–Jul. This recently
described (Smith 2001) species was long considered part of E. acutisquamata (which is here
treated as E. compressa var. acutisquamata); these two similar species differ as indicated in the
key. According to Smith (2002d), “Eleocharis occulta is very invariable in contrast to the extreme
variability of E. compressa.”
Eleocharis palustris (L.) Roem. & Schult., (marsh-loving), COMMON SPIKE-RUSH, MARSH SPIKE-
RUSH. Rhizomatous perennial, mat-forming; culms terete or slightly compressed, 30–115 cm tall,
1.5–4.5 mm wide; distal leaf sheath apex angled to a short broad point; spikelets 5–25 mm long,
with 30–100 scales; achenes biconvex, 1.1–1.9 mm long, straw-colored to dark brown; tubercle
0.3–0.7 mm long, basally constricted. Wet soils or shallow water; included based on citation for
TX by Smith (2002d); we have seen no East TX material that is undisputedly E. palustris and
thus only tentatively include the species as a member of the flora. However, the “E. palustris
complex” (see discussion below and map) is found nearly throughout TX; widespread in
Canada and throughout most of the U.S. except the extreme se. May–Jun, sporadically to Oct.
This species is part of the very difficult “E. palustris complex,” which in TX includes E.
erythropoda, E. macrostachya, and E. palustris (Smith 2002d). Smith (2002d) noted that preliminary
work indicates that “unstable chromosome structure and number as well as interspecific
hybridization contribute to the taxonomic complexity of the E. palustris complex.” See E.
macrostachya for more discussion. Due to uncertainty regarding species limits, all TX members
of the E. palustris complex are tentatively mapped together as E. palustris (which is the oldest
name). The characters used in the key to separate E. erythropoda, E. macrostachya, and E.
palustris are from Smith (2002d)—further research will be needed to determine their applicability
to TX material, and it is possible that in the future only a single species will be recognized
in the state. [Scirpus palustris L., E. smallii Britton]
Eleocharis parvula (Roem. & Schult.) Link ex Bluff, Nees, & Schauer, (very small), DWARF SPIKE-
RUSH, SMALL SPIKE-RUSH, LITTLE-HEAD SPIKE-RUSH. Plant often very small, 2–7(–12) cm tall, form-