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

576 CYPERACEAE/CYPERUS
Cyperus odoratus L., (fragrant), FRAGRANT FLAT SEDGE, LARGE-HEAD FLAT SEDGE, RUSTY FLAT
SEDGE. Tufted annual or perennial usually 5–60(–90) cm tall; inflorescences with spikelets in
dense to loose, cylindric to ovoid spikes; spikelets at maturity often dull reddish to brownish;
spikelet axis separating at maturity at the floret nodes (because this is not always evident in
young material, C. odoratus can also be reached in the key without recognizing this character);
scales relatively small, usually 1.5–3 mm long; achenes (1–)1.2–1.5(–2) mm long. Stream banks,
lake shores, or other moist areas; abundant in all parts of TX; se Canada and throughout the e
1/2 of the U.S., scattered to the w. Jun–Oct. [C. engelmannii Steud., C. ferruginescens Boeck., C.
odoratus var. engelmannii (Steud.) R. Carter, S.D. Jones, & Wipff, C. odoratus var. squarrosus
(Britton) S.D. Jones, Wipff, & R. Carter] The spongy thickened rachilla internodes have been
suggested as an adaptation “to make the achenes buoyant, thus contributing to dispersal by
water” (Tucker 1987). This is one of the most common Cyperus species in East TX. We are following
a variety of sources (e.g., Correll & Johnston 1970; Kartesz 1994, 1999; Tucker 1984b,
1994; Tucker et al. 2002) in treating it as a single variable species. Tucker (1983, 1987), for example,
indicated that there was not a single consistent character separating C. engelmannii
from C. odoratus and that the two intergrade extensively. Correll and Johnston (1970) noted
concerning C. odoratus that “… it is impossible to distinguish segregate taxa.” Given that the varieties
overlap morphologically and are mostly sympatric, treatment as a variable species without
infraspecific taxa is possibly best. Jones et al. (1996), however, recognized the following three
varieties indicating that “We find these three taxa closely related and mostly sympatric, but
discrete. Although some intermediates exist, they are relatively few. Considering their distinct
morphologies, we believe that varietal rank under C. odoratus is warranted….” For those wishing
to distinguish varieties, the following key, modified from Jones et al. (1996) and O’Neill (1940), is
provided.
1. Scales near the middle of the spikelet (2.7–)2.8–3.2 mm long; rachilla wings reaching or covering
the shoulders of the achene; achenes (1.2–)1.3–1.5 mm long, (0.5–)0.6–0.7 mm wide; spikelets
brownish ____________________________________________________________________ var. odoratus
1. Scales near the middle of the spikelet (2–)2.3–2.5(–2.6) mm long; rachilla wings rarely reaching
and never covering the shoulders of the achene; achenes 0.8–1(–1.1) mm long, (0.3–)0.4–0.5
mm wide; spikelets reddish.
2. Tip of scale reaching only to base of the scale next above on the same side of the rachis
__________________________________________________________________________ var. engelmannii
2. Tip of scale conspicuously reaching over the base of the scale next above on the same side of
the rachis ___________________________________________________________________ var. squarrosus
Cyperus oxylepis Nees ex Steud., (sharp-scaled), SHARP-SCALE FLAT SEDGE. Tufted perennial, viscid
when fresh; culms usually 50 cm or less tall; inflorescences with spikelets in ovoid, almost
head-like spikes; spikelets strongly compressed, usually 2.5–4 mm wide; achenes ellipsoid, usually
2–2.4 mm long. Ditches, other wet areas; Brazos, Hardin, Harris, Houston, Jasper, Orange,
Trinity, and Wood (Turner et al. 2003) cos.; mainly Gulf Prairies and Marshes; se U.S. from SC s
to FL w to AR and TX. Jun–Nov. Native of South America. According to Tucker et al. (2002), this
species “is easily recognized by its sticky leaves, culms, and bracts (in living plants), involute
leaves, and golden brown spikelets.” It is similar to C. elegans, which is also sticky with involute
leaves, but it can be distinguished by its ellipsoid (vs. obovoid in C. elegans) achenes. I
Cyperus plukenetii Fernald, (for Leonard Plukenet, 1642–1704, one of the original describers
and illustrators of American plants), PLUKENET’S FLAT SEDGE. Tufted perennial 30–100 cm tall;
culm bases hard, swollen, sometimes developing short knotty rhizomes; culms rough to the
touch, with minute antrorse teeth; inflorescence with longest bract usually � equal to or
shorter than longest ray; spikes with spikelets � perpendicular to the spike axis to markedly
reflexed, enough of them reflexed to give the general appearance of the spikelets drooping