1. Sparganium L. (bur‑reed)

(Cook and Nicolls, 1986, 1987)

Plants perennial, with rhizomes, monoecious. Leaves alternate, 2‑ranked, linear, the bases sheathing, the blades sometimes spongy‑thickened, parallel‑veined, usually with a pronounced midrib or keel. Flowers grouped into dense heads, these alternate, usually subtended by leaflike bracts, sessile (stalked elsewhere) along the often flexuous upper stems, the staminate heads above the pistillate heads, the individual flowers tiny, with small bracts similar to the tepals. Staminate flowers with 1–6 oblong to spathulate, scalelike tepals and 1–8 stamens, the filaments sometimes united toward the base. Pistillate flowers with 3–6 linear to spathulate, scalelike tepals and 1 superior ovary with 1 or 2 locules. Styles 1 per carpel. Stigmas 1 or 2 per carpel, oblique, linear. Fruits drupelike with spongy layers surrounding the 1 seed, the style persisting as a beak. Fourteen species, nearly throughout the Northern Hemisphere, also in Australia, New Zealand, New Guinea.

The fruits of Sparganium species are eaten by waterfowl and are apparently also dispersed by floating on water.