Sparganium hyperboreum

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.

Phenology: Flowering summer (Jul–Aug).
Habitat: Cold, quiet, shallow, oligo- to mesotrophic arctic-alpine waters
Elevation: 0–3000 m

Distribution

• Generated Map
• Legacy Map

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.

Discussion

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).

Selected References

Beal, E. O. 1977. A Manual of Marsh and Aquatic Vascular Plants of North Carolina, with Habitat Data. Raleigh. [North Carolina Agric. Exp. Sta. Techn. Bull. 247.]

Brayshaw, T. C. 1985. Pondweeds and Bur-reeds, and Their Relatives: Aquatic Families of Vascular Plants in British Columbia. Victoria. [Brit. Columbia Prov. Mus., Occas. Pap. 26.]

Cook, C. D. K. 1985. Sparganium: Some old names and their types. Bot. Jahrb. Syst. 107: 269--276.

Müller-Doblies, D. 1970. Taylor, R. L. and G. A. Mulligan. 1968. Flora of the Queen Charlotte Islands. Part 2. Cytological Aspects of the Vascular Plants. Ottawa.

Löve, Á. and D. Löve. 1981. In: IOPB chromosome number reports LXXII. Taxon 30: 694--708.

Larson, G. E. 1993. Aquatic and Wetland Vascular Plants of the Northern Great Plains. Fort Collins, Colo. [U.S.D.A. Forest Serv., Gen. Techn. Rep. RM-238.]

Mason, H. L. 1957. A Flora of the Marshes of California. Berkeley.

Voss, E. G. 1966. Nomenclatural notes on monocots. Rhodora 68: 435--463.

Lower Taxa

None.