I. Flowers all perfect, rarely some of them with stamens or pistal abortive; spikes all of one sort.

Tribe I. SCIRPEÆ. Spikelets mostly many-flowered, with only 1 (rarely 2) of the lower scales empty.

[*] Scales of the spikelet strictly 2-ranked, conduplicate and keeled.

[+] Flowers destitute of bristles and of beak to the achene, inflorescence terminal.

1. Cyperus. Spikelets few–many-flowered, usually elongated or slender.

2. Kyllinga. Spikelets 1-flowered (but of 3 or 4 scales), glomerate in a sessile head.

[+][+] Flower furnished with bristles; achene beaked; inflorescence axillary.

3. Dulichium. Spikelets 6–10-flowered, slender, clustered on an axillary peduncle.

[*][*] Scales of the several–many-flowered spikelet imbricated all round (subdistichous in n. 5).

[+] Achene crowned with the bulbous persistent base of the style (usually deciduous in n. 7); flowers without inner scales (bractlets).

[++] Hypogynous bristles (perianth) generally present; culm naked.

4. Eleocharis. Spikelets solitary, terminating the culm. Stamens 3.

[++][++] Bristles always none; culm leafy.

5. Dichromena. Spikelets crowded into a leafy-involucrate head, laterally flattened, the scales more or less conduplicate and keeled. Many of the flowers imperfect or abortive.

6. Psilocarya. Spikelets in broad open cymes. Style almost wholly persistent.

7. Fimbristylis. Spikelets in an involucrate umbel. Culm leafy at base. Style usually wholly deciduous.

[+][+] Style not bulbous at base.

[++] Flowers without inner scales, but bristles generally present.

8. Scirpus. Spikelets solitary or clustered, or in a compound umbel, the stem often leafy at base and inflorescence involucrate. Barbed bristles 3–8 or none. Stamens mostly 3.

9. Eriophorum. As Scirpus, but the bristles naked, exserted and often silky in fruit. Stamens 1–3.

[++][++] Flower with one or more inner scales.

10. Fuirena. Scales of the spikelet awned below the apex. Flower surrounded by 3 stalked petal-like scales alternating with 3 bristles.

11. Hemicarpha. Flower with a single very minute hyaline scale next the axis of the spikelet; bristles none.

12. Lipocarpha. Flower enclosed by 2 inner scales, one next the axis, the other in front of the achene; bristles none.

Tribe II. RHYNCHOSPOREÆ. Spikelets mostly 1–2-flowered, with 2–many of the lower scales empty.

13. Rhynchospora. Spikelets terete or flattish; scales convex, either loosely enwrapping or regularly imbricated. Achene crowned with a persistent tubercle or beak, and commonly surrounded by bristles.

14. Cladium. Spikelets terete, few-flowered, the scales, etc., as in the preceding. Achene destitute of tubercle. No bristles.

II. Flowers unisexual.

Tribe III. SCLERIEÆ. Flowers monœcious; the staminate and pistillate in the same or in different clustered spikes. Achene naked, bony or crustaceous, supported on a hardened disk.

15. Sclerlia. Spikes few-flowered; lower scales empty. No bristles or inner scales.

16. Carex. Hypogynous bristle short and enclosed in the perigynium or none.

[*] Stamen 1; spikelets short and small (1½–5´´ long) in globular heads, ovate or linear-oblong, many-flowered; achene oblong-obovate to linear.

[+] Low annuals; involucre 2–3-leaved; heads few; scales pointed.

6. C. aristàtus, Rottb. Dwarf (1–5´ high); spikelets chestnut-brown, oblong becoming linear, 7–13-flowered, in 1–5 ovate heads (sessile and clustered, or short-peduncled); scales nerved, tapering to a long recurved point; achene oblong-obovate, obtuse. (C. inflexus, Muhl.)—Sandy wet shores; common. Sweet-scented in drying.

7. C. acuminàtus, Torr. Slender (3–12´ high); spikelets ovate, becoming oblong, 16–30-flowered, pale; scales obscurely 3-nerved, short-tipped; achene oblong, pointed at both ends.—Low ground, Ill. and southwestward.

[+][+] Tall perennial (1–4° high); heads many, greenish; scales pointless.

8. C. calcaràtus, Nees. Culm obtusely triangular; leaves and involucre very long, keeled; umbel compound, many-rayed; spikelets ovate (1½´´ long), in numerous small heads; achenes pale, linear, on a slender stipe; scales narrow, acutish, obscurely 3-nerved. (C. virens, Gray, in part; not Michx. C. Luzulæ, var. umbellatus, Britt.)—Wet places, Del. to Fla. and Tex.

[*][*] Stamens 3 (2 in C. fuscus); spikelets clustered on the rays of a simple umbel (or in a single sessile head); scales mostly green or greenish and many-nerved, abruptly sharp-pointed; achene obovate, sharply triangular.

[+] Low annuals.

9. C. Compréssus, L. Culms 3–9´ high, with a simple sessile or a few umbellate clusters of oblong to linear spikelets (15–30-flowered and 3–8´´ long) with crowded strongly keeled and very acute pale scales.—Sterile fields along the coast, Md. to Fla. and Tex.; also adventive near Philadelphia.

C. fúscus, L. Of similar habit; spikelets much smaller (2–4´´ long), the thin brown scales (greenish only on the keel) barely acutish and very faintly nerved.—Revere Beach, Mass. (Young); on ballast at Philadelphia. (Adv. from Eu.)

[+][+] Perennial, propagating from hard clustered corms or bulb-like tubers.

10. C. Schweinítzii, Torr. Culm rough on the angles (1–2° high); umbel 4–8-rayed, rays very unequal, erect; spikelets loosely or somewhat remotely 6–12-flowered, with convex many-nerved scales; joints narrowly winged.—Dry sandy shores and ridges, western N. Y. and Penn. to Minn. and Kan.

11. C. filicúlmis, Vahl. Culm slender, wiry, often reclined (8–15´ high); leaves linear (½–2´´ wide) or filiform; spikelets numerous and clustered in one sessile dense head, or in 1–7 additional looser heads on spreading rays of an irregular umbel; joints of the axis naked; scales blunt, greenish.—Dry sterile soil; common, especially southward.

12. C. Gràyii, Torr. Culm thread-form, wiry (6–12´ high); leaves almost bristle-shaped, channelled; umbel simple, 4–6-rayed; spikes 5–10 in a loose head, spreading; joints of the axis winged; scales rather obtuse, greenish-chestnut-color.—Barren sands, Plymouth, Mass., to N. J., near the coast.

[*] Wings of the rhachis soon separating to the base as a pair of free scales; annual.

13. C. erythrorhìzos, Muhl. (Pl. 1, fig. 5–8.) Culm obtusely triangular (3´–3° high); umbel many-rayed; involucre 4–5-leaved, very long; involucels bristle-form; spikelets very numerous, crowded in oblong or cylindrical nearly sessile heads or spikes, spreading horizontally, linear, flattish (3–6´´ long), bright chestnut-colored; scales lanceolate, mucronulate.—Alluvial banks, L. I. to Penn., Mich., Minn., and southward; also adventive in N. Eng.

[*][*] Wings of the rhachis persistently attached; perennial by slender running rootstocks.

[+] Achene round-obovate; scales mucronate or acute, free or spreading.

14. C. Háspan, L. Culms sharply angled (1–1½° high); leaves linear, often reduced to membranous sheaths; umbel spreading, the filiform rays mostly longer than the 2-leaved involucre; spikelets narrowly linear; scales light reddish-brown, oblong, mucronate, 3-nerved.—Ponds and ditches, Va. to Fla. and Tex.

15. C. dentàtus, Torr. (Pl. 1, fig. 9.) Culms slender (1° high); leaves rigid and keeled; umbel erect, shorter than the 3–4-leaved involucre; scales reddish-brown, with green keel, ovate, acute, 7-nerved.—Sandy swamps, N. Eng. and northern N. Y. to S. C. and W. Va. Spikes often abortive and changed into leafy tufts.

[+][+] Achene linear to oblong; scales appressed, pointless or nearly so.

[++] Perennial by tuberiferous stolons.

16. C. rotúndus, L. (Nut-grass.) Culm slender (½–1½° high), longer than the leaves; umbel simple or slightly compound, about equalling the involucre; the few rays each bearing 4–9 dark chestnut-purple 12–40-flowered acute spikelets (4–9´´ long); scales ovate, closely appressed, nerveless except on the keel.—Sandy fields, Va. to Fla. and Tex.; also adventive near Philadelphia and New York city. (Eu.)

17. C. esculéntus, L. Culm (1–2½° high) equalling the leaves; umbel often compound, 4–7-rayed, much shorter than the long involucre; spikelets numerous, light chestnut or straw-color, acutish, 12–30-flowered (4–7´´ long); scales ovate or ovate-oblong narrowly scarious-margined, nerved, the acutish tips rather loose; achene oblong-obovate. (C. phymatodes, Muhl.)—Low grounds, along rivers, etc., N. Brunswick to Fla., west to Minn, and Tex.; spreading extensively by its small nut-like tubers and becoming a pest in cultivated grounds.

[++][++] Perennial, propagating by corm-like tubers from the base; spikelets narrow, acuminate, often teretish; scales oblong-lanceolate; achene linear-oblong.

18. C. strigòsus, L. Culm mostly stout (1–3° high); most of the rays of the umbel elongated (1–5´), their sheaths 2-bristled; spikelets 5–25-flowered, spreading; scales several-nerved, much longer than the achene.—Damp or fertile soil, Canada to Fla., west to Minn., Tex., and the Pacific. Very variable in the number and length of the rays of the simple or compound umbel, and in the size of the spikelets (2½–6 or even 12´´ long), more or less densely crowded on the axis.

19. C. speciòsus, Vahl. Culm stout, mostly low (5–20´ high); rays of the simple or compound umbel mostly all short and crowded; spikelets 10–20-flowered, yellowish-brown at maturity (3–7´´ long), the short joints of its axis winged with very broad scaly margins which embrace the ovate triangular achene; the scales ovate, obtusish, imbricately overlapping. (C. Michauxianus, Gray, Manual; not Schultes.)—Low grounds and sandy banks, N. Eng. to Fla., west to Minn. and Tex.

20. C. Engelmánni, Steud. Resembles n. 19; but the spikelets more slender and terete, somewhat remotely 5–15-flowered, the zigzag joints of the axis slender and narrowly winged, and the oblong or oval broadly scarious scales proportionally shorter, so as to expose a part of the axis of each joint, the successive scales not reaching the base of the one above on the same side; achene oblong-linear, very small.—Low grounds, Mass. to Wisc. and southward.

§ 5. MARÍSCUS. Spikelets 1–4-flowered, subterete, usually in dense heads; scales oppressed, several-nerved, the lower empty and often persistent after the fall of the rest of the spikelet; joints of the rhachis winged, enclosing the triangular achene. Perennial.

[*] Spikelets slender and acuminate, more or less refracted in usually close umbelled spikes.—Connecting with § 4.

21. C. Lancastriénsis, Porter. Culm (1–2° high) triangular; leaves rather broadly linear; umbel of 6–9 mostly elongated rays; spikelets very numerous in short-oblong close heads, soon reflexed, of 3–6 narrow scales, the upper and lower empty, twice the length of the linear-oblong achene, which is nearly 1´´ long.—Rich soil, Penn. and N. J. to Ala.

22. C. retrofráctus, Torr. Culm and leaves usually minutely downy and rough on the obtusish angles (1–3° high); umbel many-rayed; spikelets slender-awl-shaped, very numerous in obovate or oblong heads terminating the elongated rays, soon strongly reflexed, 1–2-flowered in the middle (3–5´´ long); scales usually 4 or 5, the two lowest ovate and empty, the fertile lanceolate and pointed, the uppermost involute-awl-shaped; achene linear, 1¼´´ long.—Sandy fields, N. J. to Fla. and Tex.

23. C. refráctus, Engelm. Culm 1–2° high; rays usually more or less elongated; spikelets very slender, in rather loose heads, divaricate or more or less reflexed, 2–4-flowered; achene linear, 1¼´´ long.—N. J. to N. C. and Mo.

[*][*] Spikelets very short, blunt, in densely compacted globose or cylindrical heads.

24. C. ovulàris, Torr. Culm sharply triangular (6´–2° high); umbel 1–6-rayed; spikelets (50–100) in a globular head, 3-flowered, oblong, blunt (1½–2´´ long); scales ovate, obtuse, a little longer than the ovate-oblong achene.—Sandy dry soil, southern N. Y. to Fla., west to Ill., Ark., and Tex.—Var. robústus, Boeckl., is a form with large heads (4–8´´ long), the spikelets 3–4-flowered. (C. Wolfii, Wood.)—Ill. to Ark., and southward.

25. C. Torrèyi, Britton. Like the last, but the heads cylindrical or oblong, spikelets usually 2-flowered, and achene linear-oblong.—L. Island to Fla., west to Tex.

2. E. equisetoìdes, Torr. Culm terete, knotted as if jointed by many cross-partitions; achene smooth (the minute reticulation transversely linear-rectangular), with a conical-beaked tubercle.—Shallow water, R. I. to Fla., west to Mich. and Tex.

3. E. quadrangulàta, R. Br. (Pl. 3, fig. 6–9.) Culm continuous and sharply 4-angled; achene finely reticulated, with a conical flattened distinct tubercle.—Shallow water, central N. Y. to Mich., and southward; rare.

§ 2. Spikelet terete and turgid-ovate, much thicker than the very slender culm; scales thin-coriaceous or firm-membranaceous, persistent, ovate; style 3-cleft; bristles stout, barbed downward (or sometimes upward), as long as the striate and pitted-reticulated triangular achene and its tubercle; culms tufted from fibrous roots, 1–2° high.

4. E. tuberculòsa, R. Br. (Pl. 3, fig. 10.) Culms flattish, striate; spikelet 3–6´´ long, many-flowered; tubercle flattish-cap-shaped, as large as the body of the achene.—Wet sandy soil, from Mass. along the coast to Fla.

5. E. tórtilis, Schult. Culms sharply triangular, capillary, twisting when dry; spikelet 2–3´´ long, few-flowered; conical-beaked tubercle much smaller than the achene. (E. simplex, Torr.)—Eastern shore of Md. to Fla.

§ 3. Spikelets terete, much thicker than the culm, many-flowered; scales imbricated in many or more than 3 ranks, thin-membranaceous or scarious, with a thicker midrib, usually brownish or purplish, sometimes deciduous.

[*] Style 2-cleft (often 3-cleft in n. 7 and 10) and the smooth achene lenticular; culms slender or thread-form, terete or compressed.

[+] Annuals; culms tufted, from fibrous roots.

6. E. capitàta, R. Br. Culms terete, ¼–8´ high or more; spikelets ovate to oblong (1–3´´ long), obtuse, 15–40-flowered; scales thickish, round-ovate, obtuse, brown or brownish with green keel and paler margins; stamens 2; achene obovate, black, about equalling the 6–8 bristles, tipped with a flattened or saucer-shaped tubercle. (E. dispar, E. J. Hill.)—In sand or gravel near sloughs, Md. (Canby) to Fla. and Tex.; N. Ind. (Hill). (S. Am., etc.)

7. E. ovàta, R. Br. Culms nearly terete, 8–14´ high; spikelet globose-ovoid to ovate-oblong, obtuse, 1–6´´ long (dull brown); scales very obtuse, densely crowded in many ranks; style 3- (rarely 2-) cleft; achene obovate with narrow base, pale-brownish, shining, shorter than the 6–8 bristles, broader than the short-deltoid, acute and flattened tubercle. (E. obtusa, Schult.)—Muddy places, N. Brunswick to Minn., south and westward. Variable as to the length of its bristles. A low form, with smaller and more narrowly obovate achenes, and the bristles very short or none, is E. diandra, Wright. A dwarf form occurs with very small and few-flowered heads. (Eu.)

8. E. Engelmánni, Steud. Like the last; spikelets usually narrowly cylindrical and acute or acutish, 2–8´´ long; achene broad and truncate, the tubercle covering the summit; bristles not exceeding the achene. (E. obtusa, var. detonsa, Gray.)—Mass. to Penn. and Mo.

9. E. olivàcea, Torr. (Pl. 2, fig. 1–5.) Culms flattish, grooved, diffusely tufted on slender matted rootstocks (2–4´ high); spikelet ovate, acutish, 20–30-flowered; scales ovate, obtuse, rather loosely imbricated (purple with a green midrib and slightly scarious margins); achene obovate, dull, abruptly beaked with a narrow tubercle, shorter than the 6–8 bristles.—Wet, sandy soil, Mass. to N. C., and western N. Y.

10. E. palsútris, R. Br. Culms nearly terete, striate, 1–5° high; spikelet oblong-lanceolate, pointed, many-flowered; scales ovate-oblong, loosely imbricated, reddish-brown with a broad and translucent whitish margin and a greenish keel, the upper acutish, the lowest rounded and often enlarged; achene rather narrowly obovate, somewhat shining, crowned with a short ovate or ovate-triangular flattened tubercle, shorter than the usually 4 bristles.—Very common, either in water, when it is pretty stout and tall, or in wet grassy grounds, when it is slender and lower. (Eu., Asia.)—Var. glaucéscens, Gray. Culms slender or filiform; tubercle narrower, acute, beak-like, sometimes half as long as the achene. With the type.—Var. cálva, Gray. Bristles none; tubercle short, but narrower than in the type.—Var. vìgens, L. H. Bailey. Culms very stout, rigid; achene more broadly obovoid. Lake Champlain and along the Great Lakes to Minn.

[*][*] Achene triangular or turgid; style 3-cleft.

[+] Bristles at least equalling the smooth achene, downwardly barbed, persistent.

11. E. rostellàta, Torr. Culms flattened and striate-grooved, wiry, erect (1–2½° high), the sterile ones reclining, rooting and proliferous from the apex (1–2° high), the sheath transversely truncate; spikelet spindle-shaped, 12–20-flowered; scales ovate, obtuse (light-brown); achene obovate-triangular, narrowed into the confluent pyramidal tubercle, which is overtopped by the 4–6 bristles.—Marshes, N. Eng. to S. C., west to Mich. and Ky.

12. E. intermèdia, Schultes. Culms capillary, wiry, striate-grooved, densely tufted from fibrous roots, diffusely spreading or reclining (6–12´ long); spikelet oblong-ovate, acutish, loosely 10–20-flowered (2–3´´ long); scales oblong, obtuse, green-keeled, the sides purplish-brown; achene obovoid with a narrowed base, beaked with a slender conical-awl-shaped distinct tubercle, which nearly equals the 6 bristles.—Wet slopes, Penn. to Iowa, north to Canada.

13. E. Torreyàna, Boeckl. Like the preceding, but more capillary and heads smaller (1½–2´´ long), sometimes proliferous, the one or more short new culms from the axil of its lowest scale, which persists as an herbaceous bract; achene very much smaller, with sharper angles and a short conical tubercle, which is hardly equalled by the 3–6 slender bristles. (E. microcarpa, var. filiculmis, Torr.)—Wet pine-barrens, N. J. to Fla.

(Addendum) 13^a. E. álbida, Torr. Like n. 12 and 13 in habit, somewhat stouter; spikelet dense, ellipsoidal or oblong, 1–4´´ long, acutish, with pale obtuse scales; achene very small, triangular-obovate, very smooth, with a broadly triangular tubercle upon a narrow base, shorter than or exceeding the reddish bristles.—Salt marshes, Northampton Co., Va. (Canby), and south to Fla. and Tex.

[+][+] Bristles 2–4, shorter than the achene, slender and fragile, or none.

14. E. ténuis, Schultes. Culms almost capillary, erect from running rootstocks, 4-angular and flattish (1° high), the sides concave; spikelet elliptical, acutish, 20–30-flowered (3´´ long); scales ovate, obtuse, chestnut-purple with a broad scarious margin and green keel; achene obovate, roughish-wrinkled, crowned with a small depressed tubercle, persistent after the fall of the scales; bristles ½ as long as the achene or none.—N. Scotia to N. C., Minn., and Mo. June.

16. E. melanocárpa, Torr. Culms flattened, grooved, wiry, erect (9–18´ high); spikelet cylindrical-ovoid or oblong, thick, obtuse, densely many-flowered (3–6´´ long); scales closely many-ranked, roundish-ovate, very obtuse, brownish with broad scarious margins; achene smooth, obovate-top-shaped, obtusely triangular, the broad summit entirely covered like a lid by the flat depressed tubercle, which is raised in the centre into a short abrupt triangular point; bristles often obsolete; achene soon blackish.—Wet sand, Mass. to Fla.

17. E. tricostàta, Torr. Culms flattish (1–2° high); spikelet soon cylindrical, densely many-flowered (6–9´´ long), thickish; scales ovate, very obtuse, rusty brown, with broad scarious margins; achene obovate, with 3 prominent thickened angles, minutely rough-wrinkled, crowned with a short-conical acute tubercle; bristles none.—N. J. to Fla.

18. E. Wólfii, Gray. Culms slender (1° high), from very small creeping rhizomes, 2-edged; spikelet ovate-oblong, acute; scales ovate-oblong, obtuse, scarious, pale purple; achene pyriform, shining, with 9 nearly equidistant obtuse ribs and transverse wrinkles between them; tubercle depressed, truncate, more or less apiculate; bristles not seen.—Wet prairies, N. Iowa and S. Minn.

§ 4. Spikelet more or less flattened, thicker than the slender or capillary culm, few–many-flowered; the thin membranaceous scales somewhat 2–3-ranked; style 3-cleft; bristles of the perianth 3–6, fragile or fugacious. Small or delicate species, differing from the last division chiefly in the flattish spikelets.

[*] Tubercle contracted at its junction with the achene.

19. E. aciculàris, R. Br. Culms finely capillary (2–8´ long), more or less 4-angular; spikelet 3–9-flowered; scales ovate-oblong, rather obtuse (greenish with purple sides); achene obovate-oblong, with 3-ribbed angles and 2–3 times as many smaller intermediate ribs, also transversely striate, longer than the 3–4 very fugacious bristles; tubercle conical-triangular.—Muddy shores, across the continent. (Eu., Asia.)

20. E. pygmæ̀a, Torr. Culms bristle like, flattened and grooved (1–2´ high); spikelet ovate, 3–8-flowered; scales ovate (greenish), the upper rather acute; achene ovoid, acutely triangular, smooth and shining, tipped with a minute tubercle; bristles mostly longer than the fruit, sometimes wanting.—Brackish marshes, from N. Brunswick to Fla.

[*][*] Tubercle continuous with the nutlet and not contracted at base.

21. E. pauciflòra, Link. Culms striate-angled, very slender (3–9´ high), scarcely tufted, on slender running rootstocks, with a short truncate sheath at base; scales of the ovate spikelet evidently 2-ranked, chestnut-brown, pointless, all flower-bearing, the two lower larger; bristles 3–6, about as long as the conspicuously beaked triangular achene. (Scirpus pauciflorus, Lightfoot.)—Wet places, N. Y. to N. Ill. and Minn., north and westward. (Eu., Asia.)

[*][*] Style 3-cleft and achene triangular; tubercle soon deciduous; spikelets smaller and fewer-flowered.

3. F. autumnàlis, Roem. & Schult. (Pl. 3, fig. 6–9.) Annual (3–16´ high), in tufts; culms flat, slender, diffuse or erect; leaves flat, acute; umbel compound; spikelets oblong, acute (1–2´´ long), single or 2–3 in a cluster; scales ovate-lanceolate, mucronate; stamens 1–3.—Low grounds, Maine to Fla., west to Ill. and La.

[*][*][*] Style 3-cleft, filiform and not ciliate; achene acutely triangular; tubercle more or less persistent.

4. F. capillàris, Gray. Low annual, densely tufted (3–9´ high); culm and leaves nearly capillary, the latter short; umbel compound or panicled; spikelets (2´´ long) ovoid-oblong; stamens 2; achene minutely wrinkled, very obtuse.—Sandy fields, N. Eng. to Fla., west to Minn., Tex., and the Pacific.

F. Váhlii, Link (F. congesta, Torr.), a diminutive southern species, with long filiform leaves, sessile capitate spikelets, narrow acuminate scales, and the style 2-cleft and not ciliate, has been found in ballast-sand along the northern coast.

[+][+] One-leaved involucre more conspicuous, and as if continuing the culm.

4. S. subterminàlis, Torr. Aquatic; culms (1–3° long, thickish-filiform) partly and the shorter filiform leaves wholly submersed, cellular; the filiform green bract 6–12´´ long, much surpassing the oblong spikelet; scales somewhat pointed; bristles 6, bearded downward, rather shorter than the abruptly-pointed achene.—Slow streams and ponds, N. Eng. to N. J., west to Mich. and N. Ind.—Var. terréstris, Paine; less tall, with firmer stem and leaves, and fruiting spike more turgid. Growing chiefly emersed; Herkimer Co., N. Y.

[*][*] Spikelets clustered (rarely only one), appearing lateral, the one-leaved involucre resembling and seeming to be a continuation of the naked culm.

[+] Culm sharply triangular, stout, chiefly from running rootstocks; spikelets many-flowered, rusty brown, closely sessile in one cluster; sheaths at base more or less leaf-bearing.

5. S. púngens, Vahl. Running rootstocks long and stout; culm sharply 3-angled throughout (1–4° high) with concave sides; leaves 1–3, elongated (4–10´ long), keeled and channelled; spikelets 1–6, capitate, ovoid, usually long, overtopped by the pointed involucral leaf; scales ovate, sparingly ciliate, 2-cleft at the apex and awn-pointed from between the acute lobes; anthers tipped with an awl-shaped minutely fringed appendage; style 2-cleft (rarely 3-cleft); bristles 2–6, shorter than the obovate plano-convex and mucronate smooth achene.—Borders of salt and fresh ponds and streams, throughout N. Am. (Eu., S. Am.)

6. S. Torrèyi, Olney. Rootstocks slender if any (so that the plant is readily pulled up from the mud); culm 3-angled, with concave sides, rather slender (2–4° high), leafy at base; leaves 2 or 3, more than half the length of the culm, triangular-channelled, slender; spikelets 1–4, oblong or spindle-shaped, acute, distinct, pale chestnut-color, long overtopped by the slender erect involucral leaf; scales ovate, smooth, entire, barely mucronate; style 3-cleft; bristles longer than the unequally triangular-obovate very smooth long-pointed achene.—Borders of ponds, brackish and fresh, N. Eng. to Penn., Mich., and Minn.

7. S. Olnèyi, Gray. Culm 3-wing-angled, with deeply excavated sides, stout (2–7° high), the upper sheath bearing a short triangular leaf or none; spikelets 6–12, closely capitate, ovoid, obtuse, overtopped by the short involucral leaf; scales orbicular, smooth, the inconspicuous mucronate point shorter than the scarious apex; anthers with a very short and blunt minutely bearded tip; style 2-cleft; bristles 6, scarcely equalling the narrowly obovate plano-convex and mucronate achene.—Salt marshes, S. New Eng. to Fla., west to the Pacific.

[+][+] Culm triangular, tall and stout, from slender running rootstocks; spikelets many-flowered, loosely umbellate or corymbed, involucellate-bracted.

8. S. Cánbyi, Gray. Culm (3–5° high) 3-angled, usually sharply so above, obtusely below, the sheath at base extended into a long slender triangular and channelled leaf (2–4° long); involucral leaf similar (4–8´ long), continuing the culm; spikelets oblong (4–6´´ long), single or sometimes proliferously 2 or 3 together, nodding on the apex of the 5–9 long filiform and flattened peduncles or rays of the dichotomous umbel-like corymb, or the central one nearly sessile; scales loosely imbricated, oblong-ovate, acute, pale, thin and scarious, with a greenish nerved back; bristles 6, firm, furnished above with spreading hairs rather than barbs, equalling the slender abrupt beak of the obovate-triangular shining achene (1½´´ long).—In a pond near Salisbury, Md.

[+][+][+] Culm terete, very tall and stout, from a deep running rootstock, leafless or very nearly so; spikelets numerous, clustered in a one-sided compound umbel-like panicle longer than the involucral leaf; involucellate bracts small, scale-like and rusty-scarious; scales of the spikelets rusty or chestnut-brown, scarious, the midrib extended into a mucronate point.

9. S. lacústris, L. (Great Bulrush.) Culm 3–9° high, ½–1´ thick at base; spikelets ovate-oblong (3–4´´ long); scales mostly a little downy on the back and ciliate; style 2-cleft; achene pale and dull, obovate with a narrowed base, plano-convex, mucronate-pointed, usually overtopped by the 4–6 slender downwardly barbed bristles. (S. validus, Vahl.)—Common everywhere in still fresh water. (Eu., Asia, etc.)

[+][+][+][+] Culms slender from an annual root, terete, plano-convex or obtusely triangular, naked; the sheaths rarely bearing a short leaf; spikelets few or several in a sessile cluster, sometimes solitary, much overtopped by the involucral leaf; bristles often few or wanting.

10. S. débilis, Pursh. (Pl. 3, fig. 1–5.) Culms obtusely triangular, with somewhat hollowed sides, 1–2° high, yellowish-green, shining; spikelets 3–12, capitate, ovate-oblong, obtuse (3–4´´ long), chestnut-brown; involucral leaf often horizontal at maturity; scales roundish; stamens 3; style 2–3-cleft; bristles 6, stout, downwardly barbed, equalling or two surpassing the obovate turgidly plano-convex (or bluntly 3-sided) abruptly mucronate-pointed smoothish achene.—Swamps, Mass. to S. C., Minn. and Neb. Aug., Sept.

11. S. Smíthii, Gray. Culms terete, slender, 3–12´ high, often leaf-bearing from the upper sheath, dull green as are the 1–3 oblong-ovate acute spikelets; involucral leaf always erect; scales oblong-oval; style 2-cleft; bristles 1 or 2 minute rudiments or none; achene somewhat lenticular, smooth, deciduous with the scales.—Wet shores, Delaware Bay to L. Ontario, Mich., N. Ind., and Ill. July.

[*][*][*] Spikelets in simple or mostly compound umbellate or cymose-panicled clusters, many-flowered, terete; involucre of mostly several flat leaves; culm tall, from tufted or running rootstocks, triangular, leafy, sedge-like; leaves rough on the margin; style mostly 3-cleft.

[+] Spikelets large (6–15´´ long); midrib of the scales extended beyond the mostly lacerate or two-cleft apex into a distinct awn.

13. S. marítimus, L. (Sea Club-Rush.) Leaves flat, linear, as long as the stout culm (1–3° high), those of the involucre 1–4, very unequal; spikelets few–several in a sessile cluster, and often also with 1–4 unequal rays bearing 1–7 ovate or oblong-cylindrical (rusty-brown) spikelets; awns of the scales soon recurved; achene obovate-orbicular, compressed, flat on one side, convex or obtuse-angled on the other, minutely pointed, shining, shorter than the 1–6 unequal and deciduous (sometimes obsolete) bristles.—Saline localities, on the coast from N. Scotia to Fla., and in the interior across the continent. (Eu.)—Var. macrostáchyos, Michx.; larger, with very thick oblong-cylindrical heads (1–1½´ long), and longer involucral leaf (often 1° long).

14. S. fluviátilis, Gray. (River C.) Culm very stout, 3–5° high; leaves flat, broadly linear (½´ wide or more), tapering gradually to a point, the upper and those of the very long involucre very much exceeding the compound umbel; rays 5–9, elongated, recurved-spreading, each bearing 1–5 ovate or oblong-cylindrical acute paler heads; scales less lacerate and awns less recurved; achene obovate, sharply and exactly triangular, conspicuously pointed, opaque, scarcely equalling the 6 rigid bristles.—Borders of lakes and large streams, W. Vt. to Conn. and Penn., west to Minn. and Iowa.

[+][+] Spikelets very numerous, small (1–3´´ long); scales mucronate-pointed or blunt; umbel-like cymose panicle irregular, compound or decompound; culm 2–5° high, unusually leafy; leaves broadly linear, green and rather soft; bristles very slender, often more or less tortuous and naked below.

15. S. sylváticus, L. Spikelets lead-colored, clustered 3–10 together at the end of the mostly slender ultimate divisions of the open decompound panicle, ovoid or lance-ovate, 2´´ long; scales bluntish; bristles 6, downwardly barbed throughout, rather exceeding the triangular short-pointed achene; style 3-cleft.—Along brooks, E. Mass. to N. Y.; rare.

Var. dígynus, Boeckl. Style 2-cleft and the achene not at all angled on the back; stamens 2, and bristles 4. (S. microcarpus, Presl.)—N. Scotia and N. Eng. to Minn., and westward.

16. S. atròvirens, Muhl. Leaves somewhat more rigid; spikelets dull greenish-brown, densely conglomerate (10–30 together) into close heads, these also usually densely clustered in a less compound panicle; scales pointed; bristles sparsely and strongly downwardly barbed above the middle, naked below, nearly straight, as long as the conspicuously pointed and obovate-oblong triangular achene.—Wet meadows and bogs, N. Scotia and N. Eng., west to Minn., Kan., and the Pacific.

5. E. Virgínicum, L. Culm rigid (2–4° high); leaves very narrowly linear, elongated, flat; spikelets nearly sessile, crowded in a dense cluster or head; wool rusty or copper-color, only thrice the length of the scale; stamen 1.—Bogs and low meadows, Newf. to Fla., west to Minn. and Neb. July, Aug.—Var. álbum, Gray, has the wool white. N. New York.

6. E. polystáchyon, L. Culm rigid (1–2° high), obscurely triangular; leaves linear, flat, or barely channelled below, triangular at the point; involucre 2–3-leaved; spikelets several (4–12), on smooth nodding peduncles, some of them elongated in fruit; achene obovate; wool white, very straight (1´ long or more).—Bogs, Newf. to Ga., Minn., and westward. June, July. (Eu.)—Var. latifòlium, Gray; peduncles rough; leaves sometimes broader and flatter.

7. E. grácile, Koch. Culm slender (1–2° high), rather triangular; leaves slender, channelled-triangular, rough on the angles; involucre short and scale-like, mostly 1-leaved; peduncles rough or roughish-pubescent; spikelets 3–7, small, when mature the copious white wool 6–9´´ long; achene elliptical-linear.—Cold bogs, Newf. to N. J., west to Minn. and Mo. Scales in our plant mostly light chestnut and about 3-nerved. June–Aug. (Eu.)

5. R. gracilénta, Gray. Culms very slender, 1–2° high; leaves narrowly linear; spikelets ovoid, in 2–4 small clusters, the lateral long-peduncled; achene ovoid, rather shorter than the bristles, about the length of the flat awl-shaped tubercle.—Low grounds, southern N. Y. and N. J. to Fla.

6. R. oligántha, Gray. Culm and leaves filiform, 6–12´ high; spikelets very few (1–4), ovate-oblong; bristles plumose below the middle; achene obovate-oblong, bearing a conical tubercle {1/3} its length.—Del. (Canby) to Fla.

[+][+] Bristles none, or 1–3 and minute; spikelets pale, 1-flowered.

7. R. pállida, M. A. Curtis. Culm (1–2° high) acutely triangular; leaves and spikelets as in the next species, but only a terminal dense cluster, which is less white or turns pale reddish-tawny; achene obovate-lenticular, tipped with a minute depressed and apiculate tubercle; the delicate bristles 4–5 times shorter or obsolete.—Bogs in pine-barrens of N. J. and N. C.

[+][+][+] Bristles long, denticulate downward, or both ways in n. 11.

[++] Spikelets white or whitish, becoming tawny with age, perfecting only a single flower; stamens usually 2; bristles 9–12, or even 20.

8. R. álba, Vahl. Culm slender (1–2° high), triangular above; leaves narrowly linear or almost bristle-form; spikelets lanceolate, densely crowded in a head-like terminal corymb and usually one or two lateral ones; achene oblong-obovate with a narrowed base, scarcely longer than the flattened-awl-shaped tubercle, shorter than the bristles.—Bogs, Newf. to Fla., west to N. Ind., Minn., and Oregon. (Eu.)

[++][++] Spikelets chestnut-colored or darker in n. 10 and 11, few–several-flowered; stamens 3; bristles usually 6.

9. R. capillàcea, Torr. Culm 6–9´ high, slender; leaves bristle-form; spikelets 3–6 in a terminal cluster, and commonly 1 or 2 on a remote axillary peduncle, oblong-lanceolate (pale chestnut-color, 3´´ long); achene oblong-ovoid, stipitate, very obscurely wrinkled, about half the length of the (6, rarely 12) stout bristles, and twice the length of the lanceolate-beaked tubercle.—Bogs and rocky river-banks, N. Vt. to Penn., west to western N. Y. and Minn.—Var. levisèta, Hill. Bristles perfectly smooth. N. W. Ind.

10. R. Knieskérnii, Carey. Culm 6–18° high, slender; leaves narrowly linear, short; spikelets numerous, crowded in 4–6 distant clusters, oblong-ovate (scarcely 1´´ long); achene obovate, narrowed at base, equalling the bristles, twice the length of the triangular flattened tubercle.—Pine-barrens of N. J. (on bog iron ore exclusively) to Va.; rare.

11. R. glomeràta, Vahl. Culm 1–3° high; leaves linear, flat; spikelets numerous in distant clusters or heads (often in pairs from the same sheath), ovoid-oblong; achene obovate, margined, narrowed at base, as long as the lance-awl-shaped flattened tubercle, which equals the always downwardly barbed bristles.—Low grounds, N. Eng. to Fla., west to Mich. and N. Ind.

§ 2. CERATOSCHŒ̀NUS. Spikelets lanceolate, acuminate, in fruit flattish, cymose-panicled, of only one perfect and 1–4 staminate flowers; scales few; bristles rigid, minutely scabrous upward; style simple or barely 2-toothed, filiform and gradually thickened downward, in fruit persistent as an exserted, slender-awl-shaped, upwardly roughened beak, several times longer than the smooth flat obovate achene; coarse perennials; spikelets in flower 4´´, in fruit including the projecting beak about 1´ long.

13. R. corniculàta, Gray. (Horned Rush.) Culm 3–6° high; leaves about 6´´ wide; cymes decompound, diffuse; bristles awl-shaped, stout, unequal, shorter than the achene.—Wet places, Penn. to Fla., west to S. Ind. and Mo.

14. R. macrostàchya, Torr. (Pl. 4, fig. 1–4.) Cymes decompound, or in the northern form somewhat simple and smaller, and the spikelets usually more clustered; bristles capillary, twice the length of the achene.—Borders of ponds, Mass. to N. J. and Fla.; rare.