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

646 CYPERACEAE/SCIRPUS
2002b, 2002c), Jones et al. (1997), and Whittemore and Schuyler (2002) in recognizing the segregates
of Scirpus at the generic level. This approach is supported by phylogenetic studies (e.g.,
Bruhl 1995; Muasya et al. 2000b) which suggest that Scirpus sensu lato is polyphyletic, being
made up of a number of superficially similar but not closely related species. According to
Yatskievych (1999), the “seeds of Scirpus species provide food for waterfowl, which disperse
these bulrushes both in mud on their feet and feathers and as undigested seeds in their droppings.”
(The Latin name of a bulrush)
REFERENCES: Beetle 1947; Schuyler 1966, 1967; Lye 1971a; Strong 1993, 1994; Bruhl 1995; Smith
1995; Smith & Yatskievych 1996; Muasya et al. 2000b; Whittemore & Schuyler 2002.
1. Perianth bristles very long, obviously and greatly exceeding the scales of spikelets in length;
mature inflorescences appearing almost woolly to the naked eye _________________________ S. cyperinus
1. Perianth bristles shorter than to slightly exceeding the scales of spikelets in length; mature inflorescences
not appearing woolly.
2. Spikelets mostly distinctly stalked, not arranged in tight clusters; scales of spikelets with prominent
green-keeled midrib; perianth bristles curled or contorted.
3. Leaves 4–8 per culm; scales of spikelets 1.7–2.5 mm long; mature spikelets usually > 2 mm
wide (from ca. 2–3.5 mm); perianth bristles without teeth; species widespread and common
in East TX _____________________________________________________________ S. pendulus
3. Leaves 10–20 per culm; scales of spikelets 1.2–1.8 mm long; mature spikelets usually 2 mm
or less wide; perianth bristles with delicate teeth in distal half; species known only from
extreme e edge of East TX ___________________________________________________ S. divaricatus
2. Spikelets sessile or nearly so in many tight head-like clusters; scales of spikelets without prominent
green-keeled midrib; perianth bristles, if present, straight or slightly curved.
4. Perianth bristles 0–3, shorter than achenes ______________________________________ S. georgianus
4. Perianth bristles usually 5 or 6, shorter than or a little longer than the achenes ___________ S. atrovirens
Scirpus atrovirens Willd., (dark green), PALE BULRUSH, DARK-GREEN BULRUSH, COMMON BULRUSH.
Rhizomatous perennial to 1.5 m tall, resembling S. georgianus; leaves usually 9(–11) or fewer,
mostly on the lower half of culm; sheaths and blades of lower leaves usually cross-septate; inflorescences
occasionally with bulbils proliferating to form leaves; spikelets 2–5(–8) mm long; n
= 28 (Schuyler 1976). Moist areas; Grayson (BRIT), Angelina, Franklin, Panola, Sabine, and San
Augustine (Turner et al. 2003) cos.; also Hemphill and Lubbock (Turner et al. 2003) cos. in the
Panhandle; se Canada and widespread in e 1/2 of the U.S., also AZ and MT. Summer. This species
is known to hybridize with S. georgianus (Whittemore & Schuyler 2002). However,
Whittemore and Schuyler (2002) noted that while the two species are similar, the characteristics
separating them remain constant even where they occur together.
Scirpus cyperinus (L.) Kunth, (resembling Cyperus), WOOLLY-GRASS BULRUSH; COTTON-GRASS
BULRUSH, WOOL-GRASS. Perennial 0.8–2 m tall, perennating by short tough rhizomes; leaves 5–
10, along most of culm; inflorescences with stalked spikelets or sessile spikelets arranged in
small clusters; spikelets 3–6(–9) mm long; n = 33 (Schuyler 1967). Wet or boggy places; widely
scattered in East TX w to Lamar (BRIT), Dallas, and Robertson (Turner et al. 2003) cos.; also
Hemphill Co. (Turner et al. 2003) in the Panhandle; se Canada and widespread in e 1/2 of the
U.S., also OR and WA. Summer. [S. cyperinus var. rubricosus (Fernald) Gilly, S. eriophorum
Michx., S. rubricosus Fernald]
Scirpus divaricatus Elliott, (spreading, widely divergent), SPREADING BULRUSH. Perennial 0.5–1.5 m
tall, not distinctly rhizomatous, perennating by basal offshoots; culms varying from erect to
sprawling; leaves present along most of culm; spikelets 4–15 mm long; n = 14 (Schuyler 1967). Wet
woods and swamps; Hardin Co. (Nixon & Ward 10906, BRIT); se U.S. from VA s to FL w to MO and
TX. This species was first reported for TX in 1982 (Nixon & Ward 1982). (TOES 1993: IV) �