690 CYPERACEJE scirpus 



ning rootstocks, 6 inches to 2 feet high, somewhat flattened above, leafy: 

 leaves nearly equalling the stem, deeply channelled or revolute, very rough 

 on the margins, sharply acute: spikelets 1-8, in a sessile cluster, ovate-oblong, 

 acute, 4-10 lines long: scales brown and shining, ovate, sharply carinate, 

 acutish; bristles 1-3, not half the length of the achene: style 2-cleft: achene 

 broadly ovate, plano-convex, acute, a line long. In alkaline soil on borders 

 of lakes, eastern Oregon to Nevada and California. 



S. lacustris L. Sp. 48. Perennial by stout rootstocks: stems stout, 

 terete, 6-12 feet high, often nearly an inch in diameter, sheathed below, the 

 the upper sheath sometimes extended into a short leaf: involucral bract stout, 

 shorter than the inflorescence: spikelets numerous, solitary or more or less 

 clustered in an irregularly compound umbel, oblong-ovate, 3-6 lines long: 

 scales broadly ovate, very obtuse to emarginate and mucronate, ciliate, often 

 pubescent, usually pale with fine brown lines; bristles usually 6, slender, 

 equalling or longer than the achene; stamens 3, style 2-cleft; achene broadly 

 obovate, rounded at the summit, abruptly short beaked. In marshes, Alaska 

 to California and the Atlantic States; also in Europe. 



-«- +- Stems acutely triangular or triquetrous. 



S. Olneyi Gray Bost. Journ. Nat. Hist, v, 238. Stem stout, 2-7 feet 

 high, from a stout running rootstock; more or less deeply triquetrous or 

 wing-angled, sheathed at base; leafless or with a few short leaves; involucral 

 bract stout, triangular, an inch or less longer than the inflorescence : spikelets 

 2-12, in a crowded sessile cluster, oblong-ovate, brown: bristles 4-6, shorter 

 than or equalling the achene: stamens 2 or 3: style 2-cleft: achene obovate, 

 plano-convex, mucronate, brown. In salt marshes, eastern oregon to Cali- 

 fornia and the Eastern States. 



S. Americanus Pers. Syn. i, 68. S. pungens Vald. Stems usually 

 slender, from long perennial rootstocks, 1-4 feet high, acutely triangular, 

 somewhat leafy at base: leaves 1-4, shorter than the stem, keeled: involucral 

 bract more or less channelled, 1-4 inches long: spikelets 1-6, closely crowded 

 in a sessile cluster, ovate to ovate-oblong: scales brown, often very dark, 

 broadlv ovate, emarginate and usually tipped with a straight awn: bristles 

 2-6, shorter than or equalling I he achene: stamens 3: style usually 2-cleft: 

 achene obovate, smooth, dark brown mucronate. Common in salt marshes, 

 throughout the United States. 



* * * Stems triangular, leafy at base: leaves flat: involucre foliaceous. 



Spikelets large, few, in a sessile cluster or sparingly umbellate, rufous. 



S. robustus Pursh Fl. 56 Stems stout, 1-3 feet high, from running 

 often tuberiferous rootstocks: leaves flat, equalling or exceeding the stem: 

 involucral bracts unequal, one much longer and more erect: spikelets ovate 

 to oblong-ovate, acute, 5-10 lines long: scales ovate, 2-3 lines long, dull 

 brown, emarginate, tipped with a long slender soon reflexed awn: bristles 

 1-6, fragile, shorter than the achene: stamens 3: style 3-cleft: achene com- 

 pressed very flat on the face, convex, or with a low ridge on the back, 

 obovate-orbicular, dark brown, shining, H lines long. In salt marshes, 

 Bri. Columbia to California and the Atlantic States. 



-«- +■ Spikelets small, numerous, greenish or light brown, in a 

 compound or decompound umbellate panicle. 



S. microcarpus Presl. Reliq. Hsenk. i, 195. S. sylvaticus var. digyrms 

 Bcekl. Stems usually stout, 3-5 feet high, from perennial rootstocks: 

 leaves ample, often exceeding the stem, rough-margined, those of the in- 

 volucre usually exceeding the inflorescence: panicle ample, decompound, 

 rather loose: spikelets ovoid, oblong, acute, 1^-2 lines long, 3-25 together 





