Scirpus hattorianus
Scirpus cyperinus
early dark-green bulrush, mosquito bulrush, scirpe de hattori
common woolly bulrush, common woolsedge, cottongrass bulrush, scirpe souchet, wool grass
fertile ones upright or nearly so;
nodes without axillary bulblets.
fertile ones upright or nearly so;
nodes without axillary bulblets.
3–9 per culm;
sheaths of proximal leaves light brown;
proximal sheaths and blades with septa few to many, rather inconspicuous;
blades 20–35 cm × 5–9 mm.
5–10 per culm;
sheaths of proximal leaves green to red-brown;
proximal sheaths and blades with septa few to many, conspiucuous or inconspicuous;
blades 22–80 cm × 3–10 mm.
terminal;
rays ascending or divaricate (usually both in the same inflorescence), rays often bearing axillary bulblets, proximal branches smooth, distal branches scabrellous to scabrous;
bases of involucral bracts green, margins usually speckled with red-brown, rarely solid black, not glutinous.
terminal;
rays ascending or sometimes spreading, scabrous throughout or main branches smooth proximally, rays without axillary bulblets;
bases of involucral bracts reddish brown, brownish, or blackish, not glutinous.
in dense clusters of 4–55 (largest cluster with 15 or more), spikelets sessile, ovoid or broadly ovoid, 2–3.5 × 1.3–2.5 mm;
scales blackish or occasionally brownish with pale midribs, elliptic or broadly elliptic, 1–1.4(–2) mm, apex mucronate, mucro 0.1–0.2 mm.
in dense cymes of 2–15, central spikelet of each cyme sessile, others sessile or pedicellate, spikelets broadly ovoid, ovoid, or sometimes cylindric, 3.5–8 × 2.5–3.5 mm;
scales reddish brown, brownish, or blackish, ovate or narrowly ovate to oblong-ovate or oblong-elliptic, 1.1–2.2 mm, apex apiculate or short-mucronate, apiculus or mucro to 0.1 mm.
perianth bristles persistent, (4–)5–6, slender, straight or curved, shorter than to equaling achene, with retrorse, thin-walled, round-tipped barbs in distal (0.1–)0.2–0.4, enclosed within scales;
styles 3-fid.
perianth bristles persistent, 6, slender, contorted, much longer than achene, smooth, projecting beyond scales, mature inflorescence appearing woolly;
styles 3-fid.
pale brown, elliptic or obovate in outline, plumply trigonous, (0.6–)0.7–1.1 × 0.3–0.5 mm.
whitish to very pale brown, elliptic or obovate in outline, plumply trigonous or plano-convex, 0.6–0.9 × 0.3–0.5 mm.
= 56.
= 66.
Scirpus hattorianus
Scirpus cyperinus
Scirpus hattorianus has been confused in the past with both S. atrovirens and S. georgianus. Scirpus hattorianus tends to be a more slender plant, and the scales of its spikelets are usually black, not brown. The perianth bristles are superficially intermediate between the other two. They are typically shorter and more delicate than those of S. atrovirens. In S. hattorianus the longest bristles are usually only 0.6–0.8 times as long as the achene, and barbed in the distal (0.1–)0.2–0.4; in S. atrovirens the longest bristles are usually 0.9–1.2 times as long as the achene and barbed in the distal 0.3–0.6. Some individuals fall outside these ranges and identification must be based on comparison of all the characters mentioned in the key. Separation from S. georgianus is discussed under S. georgianus.
Scirpus hattorianus occasionally hybridizes with S. ancistrochaetus, S. atrocinctus, S. atrovirens, S. georgianus, and S. pedicellatus. The name Scirpus peckii Britton has been applied to hybrids between S. hattorianus and S. atrocinctus or S. pedicellatus.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Scirpus cyperinus is extremely variable. A form common in the northern part of its range, south to Iowa, northern Ohio, Maryland, and (in the Appalachians) North Carolina and Tennessee, has bases of the involucral bracts and the involucels blackish, the spikelets sessile or nearly so in glomerules, and the scales relatively short, ovate, and brownish. This form has often been treated as S. cyperinus var. pelius. A more robust southern form, extending north to southern Missouri and Illinois, Kentucky, Virginia, and (along the coast) New Jersey and Massachusetts, has the bases of the involucral bracts and the involucels reddish brown, the spikelets mostly solitary, and the scales relatively long, narrowly elliptic, and reddish brown. This form has often been treated as a distinct species, S. rubricosus (or under the illegitimate name S. eriophorum Michaux). These two morphologies intergrade so extensively that it is not practical to recognize them taxonomically at any rank.
Scirpus cyperinus often hybridizes with S. atrocinctus and S. pedicellatus, forming hybrid swarms. Some plants appear to have characteristics of all three species; the names Scirpus atrocinctus var. grandis Fernald and S. atrocinctus forma grandis (Fernald) D. S. Carpenter are based on such a specimen.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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