Sparganium glomeratum
Sparganium hyperboreum
cluster bur-reed, northern bur-reed, rubanier aggloméré
northern bur-reed, rubanier hyperboréal
stiff, weakly keeled, to 50 cm × 6 mm.
limp, unkeeled, flat, 0.1–0.4(–0.8) m × 1–5 mm.
rachis unbranched, condensed, erect;
bracts ascending, somewhat inflated near base; pistillate heads 2–6, mostly supra-axillary, sometimes opposite bract above, upper crowded, sessile, proximal head not contiguous with upperdistal, peduncled, 1.2–1.6(–2) cm diam. and contiguous in fruit; staminate heads 1(–2), contiguous or not with distalmost pistillate head.
rachis unbranched, flexuous;
bracts ascending, lower bracts slightly inflated near base; pistillate heads 1–4, axillary, contiguous, sessile, or most proximal peduncled and supra-axillary, 0.5–1.4 cm diam. in fruit; staminate heads 1(–2), terminal, contiguous or not with distalmost pistillate head.
tepals without subapical dark spot, entire to erose;
stigma 1, lanceolate.
tepals without subapical dark spot, erose;
stigmas 1, ovate.
greenish brown, lustrous, stipitate, fusiform, body not faceted, slightly constricted near equator, 3–6 × 2–3 mm, tapering to beak;
beak straight, 1.5–2 mm;
tepals attached at base, reaching 1/3 to 1/2 length of fruit.
brown or yellowish, dull, subsessile, body ellipsoid to obovoid, not faceted, ±more or less constricted at equator, 2–5 × 1.5–2.5 mm;
beak less than 0.5 mm, or absent;
tepals attached at base, not reaching equator.
1.
1.
= 30.
= 30.
Sparganium glomeratum
Sparganium hyperboreum
Sparganium glomeratum is apparently rare, or perhaps is only rarely collected, in North America, except it is locally common in sedge-marshes and black-ash swamps near the western end of Lake Superior. The species is rather invariable throughout its circumboreal range (C. D. K. Cook and M. S. Nicholls 1986).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Sparganium hyperboreum is distinguished from other floating-leaved species by its beakless fruits with sessile stigmas.
Putative hybrids between Sparganium hyperboreum and S. natans have been found in Manitoba, Newfoundland, Northwest Territories, and Alaska by V. L. Harms (1973), who discussed variation in both species. The hybrids have wider (2–5 mm) leaves, golden-brown fruits with short (1 mm) beaks, and supra-axillary pistillate heads (V. L. Harms 1973; C. D. K. Cook and M. S. Nicholls 1986).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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USDA Plants Database
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