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

ELEOCHARIS/CYPERACEAE
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ing mats; rhizomes short, terminating in small tubers (0.5–1.5 mm in diam.); distal leaf sheath
apex thinly membranous, often disintegrating, angled to a short broad point on one side; spikelets
often very small, 2–5(–6) mm long, with 6–25 scales; achenes trigonous, 0.8–1.1 mm long
including confluent tubercle, straw-colored to light to dark brown; tubercle scarcely recognizable
as separate except under high magnification, 0.3 mm or less long. In mud, often in alkaline
soils; widely scattered in TX; s Canada and widespread in the U.S. Apr–Aug. [E. coloradoensis
(Britton) Gilly, E. parvula var. coloradoensis (Britton) Beetle, E. parvula var. anachaeta (Torr.)
Svenson, Scirpus coloradoensis Britton, Scirpus nanus Spreng., Scirpus parvulus Roem. &
Schult.] While we are not separating it pending further study (following Yatskievych 1999),
Smith (2002d) distinguished E. coloradoensis and indicated that it, rather than E. parvula, occurs
in TX. He separated this taxon from E. parvula as follows:
1. Perianth bristles present or very rarely absent, the longer equaling achene or exceeding tubercle;
tubers (except buds) oblong, usually markedly curved; achenes smooth or faintly rough
at 30�; floral scales 6–10 per spikelet ___________________________________________________ E. parvula
1. Perianth bristles absent or not more than 1/2 length of achene; tubers (except buds) obovoid to
orbicular, not markedly curved, 0.7–1.5 mm thick; achenes clearly rugulose at 10� to finely rough
at 30�; floral scales 6–25 per spikelet ______________________________________________ E. coloradoensis
Eleocharis quadrangulata (Michx.) Roem. & Schult., (four-angled), SQUARE-STEM SPIKE-RUSH.
Coarse rhizomatous perennial; culms erect, to 80(–150) cm tall, distinctly 4-sided, with incomplete
transverse septa; distal leaf sheath apex with one side long acute to acuminate; spikelets
linear-cylindric, usually (15–)20–42(–50) mm long, with (28–)40–90(–135) scales, the scales often
persistent (unusual in that most species shed their scales as the fruits mature); achenes biconvex,
ca. 2–3 mm long, usually yellowish to brown, reticulate when observed with a hand
lens; tubercle longer than broad, 0.7–1.5 mm long, constricted basally, often dark though sometimes
whitish. Mud, lake margins; widespread in e 1/2 of TX; se Canada (Ont.) and most of the e
U.S., also CA and OR. Apr–Sep. [E. quadrangulata var. crassior Fernald, Scirpus quadrangulatus
Michx.] m/285
Eleocharis radicans (Poir.) Kunth, (rooting), ROOTED SPIKE-RUSH. Diminutive rhizomatous perennial,
forming mats; culms very soft and spongy, 1–12 cm tall; distal leaf sheath with apex membranous,
blunt; spikelets 2–3(–4) mm long, ovoid, with 5–15 scales; anthers very small, 0.3–0.5
mm long; achenes obscurely trigonous to subterete, 0.7–0.9 mm long, grayish to brownish, longitudinally
ridged, with many fine horizontal lines between the ridges; tubercles ca. 0.15 mm
long. Margins of lakes, bogs, seeps, other wet areas, sometimes submerged; Harris, Leon (BRIT),
Gonzales, Grayson, Red River, and Robertson (Turner et al. 2003) cos.; AZ, CA, FL, LA, MI, OK,
TX, and VA. Apr–Nov. [E. acicularis (L.) Roem. & Schult. var. radicans (Poir.) Britton, E.
lindheimeri Svenson, Scirpus radicans Poir.]
Eleocharis ravenelii Britton in Small, (for its collector, H.W. Ravenel, 1814–1887), RIO GRANDE
SPIKE-RUSH, SOUTH TEXAS SPIKE SEDGE. Perennial, with rhizomes, but these often not obvious;
culms 20–55 cm tall, hollow, with complete septa internally, but these not visible externally;
distal leaf sheath apex with a red or brown margin, � perpendicular to culm, with an abrupt
awl-shaped tooth on one side; spikelets 5–13 mm long, lanceoloid, with 10–100 scales, these 1–1.5
mm long; achenes compressed trigonous or some biconvex, 0.6–0.8 mm long, green to brown;
tubercle 0.1–0.2 mm long, wider than long. Seasonally wet areas, ditches, low woods; Guadalupe
Co. (Turner et al. 2003 as E. austrotexana) near sw margin of East TX; otherwise known in TX
from only a few counties in the Gulf Prairies and Marshes and South TX Plains (Carr 2001;
Turner et al. 2003); in the U.S. known only from TX. Spring-fall. [E. austrotexana M.C. Johnst.]
This species has long gone under the name of E. austrotexana (e.g., Correll & Johnston 1970;
Hatch et al. 1990). However, Smith (2002d) indicated that the holotype of E. ravenelii appears
conspecific with E. austrotexana. We are therefore following Smith (2002d) in using the older