Sparganium fluctuans (Engelm.) B. L. Rob.

The tepals are usually adnate to the fruit stipe for about half their length, but in our other species they are free from it.

Sparganium fluctuans is not known to hybridize. When vegetative, it is sometimes confused with S. angustifolium, but the floating leaves of that species are usually less than 5 mm wide and plano-convex. Sparganium fluctuans is more robust than the grasslike S. natans, with which it sometimes grows.

Plants limp, to more than 1 m long; leaves and inflorescences floating. Leaves limp, unkeeled, flat, mostly 0.6--1 m  4--10 mm. Inflorescences: rachis 0--2-branched, distal part erect at water surface; bracts ascending, not inflated at base; pistillate heads 0--2 on main rachis, 1--2 on secondary rachises, axillary or supra-axillary, often some contiguous or nearly so, especially in fruit, sessile, 1.5--2.3 cm diam. in fruit; staminate heads 3--6 on main rachis, 1--4 on secondary rachises, contiguous or not, but not contiguous with distalmost pistillate head. Flowers: tepals often with prominent apical dark spot, apically erose to fimbriate; stigmas 1, linear-lanceolate. Fruits eventually dark reddish brown, dull, stipitate, elliptic to obovoid or fusiform, body not faceted, sometimes constricted near equator, 2--5  1.5--2 mm, tapering to beak; beak curved, 2--3.5 mm; tepals borne at middle of fruit stipe, basally adnate to stipe, reaching about nearly to equator. Seeds 1.

Alta, B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.S., Ont., P.E.I., Que., Sask.; Conn., Maine, Mass., Mich., Minn., N.H., N.J., N.Y., Pa., Vt., Wis.

Flowering summer (Jul--Aug).

Quiet, cold, acidic -to -neutral oligotrophic waters to 2 m deep but usually less, abundant in some areas but not in others, sometimes covering the water with its strap-shaped leaves; 0--600m.

Sparganium androcladum (Engelmann) Morong var. fluctuans Engelmann ex Morong, Bull. Torrey Bot. Club 15: 78. 1888

Sparganium fluctuans (Morong) B. L,. Robinson, Rhodora 7 : 60. 1905
Sparganium simplex fluiians Engelm.; A. Gray Man. ed. 5. 481. 1867. Sparganium androcladum fluctuans Morong, Bull. Torrey Club 15 : 78. 1888.
Perennial, with a rootstock and numerous roots at the base of the stem ; stem slender, floating, 3-15 dm. long ; leaves only slightly if at all carinate, 3-6 dm. long, 3-11 mm. wide, cellular-reticulate ; bracts 3-12 cm. long, dilated and somewhat scarious-margined towards the base ; inflorescence usually branched ; branches usually with 1 pistillate and 2 staminate heads, the main axis with 2-4 staminate heads ; fruiting heads about 2 cm. in diameter ; sepals spatulate, erose at the apex, almost without a distinction between blade and claw ; body of the brown achenes fusiform, sometimes constricted at the middle; stipe short; beak about 2 mm, long, curved ; stigma short, oblique, oblong ; anthers oblong, about one third as broad as long.
Type locality : Ponds at the base of the White Mountains [New Hampshire] . Distribution : Cold lakes and ponds, from Maine to Connecticut and Minnesota.

Sparganium fluctuans is a species of bur-reed found in North America known by the common name floating bur-reed. It is listed as endangered in Connecticut.

Sparganium fluctuans là một loài thực vật có hoa trong họ Typhaceae. Loài này được (Engelm.) B.L.Rob. miêu tả khoa học đầu tiên năm 1905.