Schoenoplectus hallii
Schoenoplectus purshianus
Hall's annual-bulrush, Hall's bulrush
scirpe de Pursh, weak-stalk annual-bulrush, weak-stalk club-rush (bulrush)
often arching to decumbent, cylindric, ridged when dry, 0.05–0.8 m × 0.5–1 mm.
often arching (to decumbent), cylindric, 0.1–1 m × 0.5–2 mm.
3–4, 1 cauline;
sheaths straw-colored to brown and disintegrating to fibers, front translucent and splitting;
blades 1–2, proximally thickly C-shaped in cross section, distally flat, from much shorter to longer than sheath, 1–200+ × 0.2–1 mm, smooth or margins distally spinulose.
1, to equaling culm;
sheath fronts not pinnate-fibrillose;
blade 0 or 1, C-shaped in cross section, from a mucro to longer than a sheath, 0.5–1 mm wide, smooth.
capitate or 1 spikelet or rarely with 1 or 2 branches to 12 mm;
proximal bract erect, resembling leaf blades, 5–150 mm.
capitate or 1 spikelet;
proximal bract erect or often divergent, subterete-channeled, on longer culms of plant 1–15 cm and 1/30–1/3 of culm length.
achenes blackish brown, plano-convex or usually the adaxial surface longitudinally concave, ovoid to obovoid, 1.3–1.7 × 1.2–1.3 mm, with 15–18 mostly sharp ridges;
beak 0.1 mm.
1–12, 5–12 × 3–4 mm;
scales straw-colored to orange-brown, often lineolate-spotted, midrib region often greenish, broadly obovate, 2.5–3 × 2.5 mm, smooth, margins ciliolate distally, flanks in proximal part of spikelet each with 2–10 distinct ribs, apex rounded, entire, mucronate.
perianth absent;
anthers 0.4 mm;
styles 2-fid.
perianth members 6, rarely absent, brown, bristlelike, equaling to slightly exceeding achene, distinctly wider proximally, densely retrorsely spinulose to appressed-spinulose;
anthers 0.5–0.7 mm;
styles 2-fid or 2-fid and 3-fid.
brown, turning blackish, thickly biconvex, sometimes plano-convex or obscurely compressed-trigonous with rounded abaxial angle, abaxial face with central bulge, obovoid, proximally rounded to distinct stipelike constriction, 1.6–2.2 × 1.2–1.5 mm, base 0.3–0.4 mm wide;
beak 0.1–0.3 mm.
achenes thickly trigonous with convex abaxial face, 1.7–2.5 × 1.1–1.6 mm, rugose with rounded ridges;
beak 0.3 mm.
= 22.
Schoenoplectus hallii
Schoenoplectus purshianus
Many reports of Schoenoplectus hallii are based on misidentified specimens of S. saximontanus or S. erectus. The Iowa specimen was probably collected in 1890. The species is probably extirpated from Massachusetts. I have identified a specimen from the Georgia coastal plain, where S. hallii and S. erectus are sympatric, as intermediate between the two.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Varieties 2 (2 in the flora).
Culms of Schoenoplectus purshianus have been described erroneously as trigonous (e.g., M. L. Fernald 1950). Schoenoplectus purshianus is widely confused with S. smithii; they are clearly distinct (M. Blondeau et al. 1996; S. G. Smith and E. Hayasaka 2002). Some authors (A. A. Beetle 1942b; H. A. Gleason 1952; H. A. Gleason and A. Cronquist 1963; E. G. Voss 1972–1996) have placed S. purshianus (as Scirpus) in synonymy under Schoenoplectus smithii, and most published distributions are erroneous. The taxonomic confusion is because of the subtle nature of the diagnostic characteristics of achenes and perianth bristles, the occurrence in both species of plants with or without bristles, and overlapping involucral bract lengths and frequency of divergence. No intermediates are known; although the two species occasionally grow together they are not known to hybridize. Close examination of the perianth bristles and achenes of S. purshianus and S. smithii reveals taxonomically useful but overlooked differences as stated in the key and summarized under S. smithii.
Schoenoplectus purshianus has also been confused with its close relatives in sect. Actaegeton: Schoenoplectus juncoides (Roxburgh) Palla, S. hotarui (Ohwi) Holub, and Scirpus rockii Kükenthal, which belong to the difficult “Scirpus juncoides complex” of eastern Asia, the Pacific islands, and eastern North America; Schoenoplectus purshianus should be treated as a distinct North American species pending further research (S. G. Smith and E. Hayasaka 2002).
The name Scirpus erectus Poiret has been widely misapplied to members of that complex (see 17. Schoenoplectus erectus). The names Scirpus smithii var. williamsii (Fernald) Beetle, S. juncoides Roxburgh var. williamsii (Fernald) T. Koyama, and Schoenoplectus smithii subsp. williamsii (Fernald) Soják were misapplied by their authors to both S. purshianus var. purshianus and S. purshianus var. williamsii.
Schoenoplectus purshianus var. williamsii in recent years has been treated as Scirpus purshianus forma williamsii (Fernald) Fernald. It seems better to treat the taxon as a variety rather than a form, pending further research, because it reportedly occurs in habitats with more water-level fluctuation than S. purshianus var. purshianus (A. E. Schuyler 1972; S. G. Smith and E. Hayasaka 2002) and thus may be useful as an ecologic indicator, and because form status suggests that the taxon is trivial.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Perianth bristles present. | var. purshianus |
1. Perianth bristles absent. | var. williamsii |
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