S. fluitans: aquatic; stems long, slender, branching, either floating in water, or forming soft densely matted masses on its margin; leaves linear-subulate; spikelets solitary, terminal, oblong, greenish, the outer bract without any leafy point. - Pools and still waters. Fl. June, July.
S. setaceus: stems slender, 2-3 inches high, forming dense tufts, with 1-2 short, subulate leaves on each stem, sheathing it at the base; spikelets ovoid, solitary, or 2-3 together in a little cluster, appearing lateral, the subulate point of the outer bract forming a continuation of the stem; glumes broad, short, dark brown, with a green midrib. - Muddy places, margins of pools, etc. Fl. July.
** Hypogynoas bristles 4-6.
S. caespitosus: stem 1/2-1 foot high, densely tufted; spike-lets solitary and terminal, ovoid, brown, the outer bract like the glumes but larger, with an almost leafy tip, about the length of the spikelet; flowers usually 6-8 in the spikelet. - Marshes and bogs. Fl. June to August.
*** Hypogynous bristles 6.
† Stem triangular; panicle leafy.
S. maritimus: stems sharply triangular, 2-5 feet high; leaves long, flat, pointed, often far exceeding the stem; spike-lets rich brown, ovoid or lanceolate, sometimes only 2-3 in a close sessile cluster, more frequently 8-10 in a compound cluster, the outer ones stalked; glumes notched, with a fine point. - Salt marshes. Fl. July.
S. sylvaticus: stems triangular, 2-3 feet high; leaves long, grass-like; spikelets ovoid, dark shining green, very numerous, in clusters of 2-3 together, forming a terminal, much branched, compound umbel or panicle, with an involucre of 2-3 linear leaves; glumes keeled and pointed. - Moist woods, and banks of rivers. Fl. July.
†† Stem triangular; panicle leafless.
S. triqueter: stems acutely triangular, 2-3 feet high, leafless; spikelets ovoid 8 - 10 or more, the central ones sessile, the others stalked, forming a compound lateral cluster or um33i Summer Flowers.
Bel, the stiff, triangular outer bract continuing the stem for an inch or more; glumes brown, broad, usually notched or fringed at the top, with a minute point. - Marshes and edges of pools. Fl. August.
††† Stem terete. S. lacustris: stems stout, erect, 2-6 or 8 feet high, cylindrical at the base, tapering upwards, sometimes obtusely triangular near the top, with a single short leaf near the base; spikelets ovoid or oblong, rather numerous, in a compound lateral umbel or cluster, the outer bract continuing the stem; glumes numerous, broad, brown, fringed at the edge, notched at the top, with a little point in the notch. - Bull-rush. - Margins of lakes and ponds. Fl. June, July.