Northern Burr Reed

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).

Plants slender, grasslike, to 0.8 m; leaves and inflorescences usually floating. Leaves limp, unkeeled, flat, 0.1--0.4(--0.8) m  1--5 mm. Inflorescences: 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. Flowers: tepals without subapical dark spot, erose; stigmas 1, ovate. Fruits 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. Seeds 1. 2n = 30.

Greenland; St. Pierre and Miquelon; Alta., B.C., Nfld. and Labr., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Yukon; Alaska; circumboreal.

Flowering summer (Jul--Aug).

Cold, quiet, shallow, oligo- to mesotrophic arctic-alpine waters; 0--3000m.

Sparganium williamsii Rydberg, sp. nov
Perennial, with a horizontal rootstock ; stem slender, ascending, about 3 dm. high ; leafblades light-green, 1-3 dm. long, 3-4 mm. wide, obtuse, cellular-reticulate, especially the lower part ; sheaths, especially those of the bracts, dilated and decidedly scariousmargined ; peduncles strict ; pistillate heads 3-4, the lower two usually on supra-axillary peduncles 1-3 cm. long, the upper sessile, in fruit 8-10 mm. in diameter ; sepals oblanceolate, gradually tapering downward, erose at the apex, about half as long as the achenes ; achenes yellowish-green, dull, ellipsoid, acute at both ends, sessile, usually somewhat constricted below the middle ; beak fully 0.5 mm. long; stigma short, ovate; staminate heads usually solitary, confluent with the upper pistillate one, or on a very short stalk ; anthers short, about half longer than broad.
Type collected at Klondike Bottom, Yukon Territory, in July, 1899, R. S. Williams (herb. N. Y. Bot. Gard.).

Sparganium hyperboreum Laest.; Beurl. Oefv. Sv. Vet.-
Akad. Forh. 9: 192. 1852.
Sparganium naians submuticum Hartm. Handb. Skand. Fl. ed. 4. 312. 1843. Sparganium submuticum Hartm. Handb. Skand. Fl. ed. 12. 108. 1889.
Sparganium angustifolium Meinsh. Mel. Biol. Acad. St. Petersb. 13: 396. 1893. Not P. angustifolium Michx. 1803.
Perennial, with a rootstock; stem slender, in deep water elongated, floating, sometimes 5 dm. long, in shallow water or mud decumbent or ascending, 1-2 dm. long ; leaves lightgreen, flat or slightly round-keeled at the base, 1-4 mm. wide, in deep water sometimes 6 dm. long ; sheaths slightly dilated but not scarious-margined ; peduncle more or less rlexuose ; pistillate heads 2-4, the lower one or two usually stalked and supra-axillary, in fruit 8-10 mm. in diameter; achenes dark-yellow, dull, ellipsoid, acute at both ends, neither stalked nor beaked; stigmas sessile, irregularly nipple-shaped ; sepals about half as long as the fruit, clawed ; blades cuneate or cuneate-spatulate, truncate ; staminate heads usually solitary, often close to the uppermost pistillate one ; anthers short, about one and a half times as long as broad.
Type locality : Manu, Tome I^apmark, Sweden.
Distribution : Greenland to Newfoundland, Hudson Bay, and Alaska ; also in arctic and subarctic Europe and Asia.