CYPERACEAE (SEDGE FAMILY) 85 



in spikes solitary or clustered upon the rays, the central spike or cluster al- 

 ways sessile, and the whole often contracted into a single more or less dense 

 head. Scales concave or keeled, often decurrent upon the rachis. Achene 

 lenticular or triangular, not beaked, usually smooth. 



Small annual; stamen 1 . . . . . . . ' . . .1. C. inflexus. 



Perennials; stamens 3. 



Spikes in a dense head 2. C. filiculmis. 



Spikes in an unequal-rayed umbel 3. C. Schweinitzii. 



1. Cyperus inflexus Muhl. Gram. 16. 1817. Low annuals, with a 2-3- 

 leaved involucre: spikes oblong, becoming linear, 7-13-flowered, in 1-5 ovate 

 heads: scales nerved, tapering into a long recurved point: stamen 1: achene 

 obovate, obtuse. C. aristatus. Said to be sweet-scented in drying. Fre- 

 quent in our range; across the continent. 



2. Cyperus filiculmis Vahl. Enum. 2: 328. 1806. Perennial, with hard 

 clustered corm- or bulb-like tubers -at the base of the stem: stem slender, wiry, 

 often reclined: leaves linear: spikes numerous and clustered in one sessile 

 dense head, or in 1 to 7 additional looser heads on spreading rays of an, ir- 

 regular umbel: joints of the axis naked: scales blunt, greenish, strongly 7-11 

 nerved: stamens 3: achenes gray, 3-angled, obtuse, apiculate. Extending 

 into Colorado from the east. 



3. Cyperus Schweinitzii Torr. Ann. Lye. N. Y. 3: 276. 1836. Perennial: 

 culms with thickened corm-like bases, rough on the angles, 2-5 dm. high: 

 leaves linear: umbel simple, 4-8-rayed: spikes crowded along the upper part 

 of the mostly elongated rays, erect: scales awl-pointed: joints at the axis 

 narrowly-winged: stamens 3: achene brown, sharply 3-angled, acute at each 

 end. Colorado, northward and eastward to New York. 



2. SCIRPUS L. RUSH. BULRUSH 



Tufted plants, with creeping rootstocks, the stem sheathed or leafy at base, 

 and the spikelets in an apparently lateral cluster, or compound umbel-like 

 panicle, or solitary. Hypogynous bristles 3-6, barbed or ciliate, or wanting. 

 Style 2-3-cleft. Achene lenticular or more or less triangular, obovoid. 



Spikelets solitary, terminal. 



Marsh plant; achene reticulated . . . . . . . 1. S. pauciflorus. 



Terrestrial plant; achene smooth . . . . . . . 2. S. caespitosus. 



Spikelets normally more than 1. 



Spikelets few-several, sessile or nearly so, in crowded capitate cluster. 



Leaves reduced to sheathing bracts at the base . . . . 3. S. Olneyi. 



Leaves well developed. 



Involucral leaves flat and broad. 



Rootstocks often tuberous; bristles longer than the achene . 4. S. paludosus. 

 Rootstocks not tuber-bearing; bristles shorter than the 



achene or wanting . . . . ' . . ..- . 5. S. campestris. 



Involucral leaves folded-triangular, narrow. 



Stem terete . . . . . . . . . 6. S. nevadensis. 



Stem sharply triangular . . . . . . . 7. S. americanus. 



Spikelets several-numerous, in unequal-rayed simple or compound 



umbellate panicles. 



Leaves reduced to sheaths or the lowest sheath developing a blade 8. S. lacustris. 

 Leaves well developed. 



Bristles more or less barbed. 

 Achene 3-angled; styles 3. 



Spikes large 9. S. fluviatilis. 



Spikes small and very numerous ..... 10. S. atrovirens. 

 Achene plano-convex, carinate on back; styles 2 . . . 11. S. microcarpus. 

 Bristles not barbed, long and tortuous ..... 12. S. lineatus. 



1. Scirpus pauciflorus Light. Fl. Scot. 1078. 1777. Perennial by filiform 

 rootstocks: stems very slender, little tufted, 1-2 dm. high, upper sheaths 

 truncate: spikelets solitary, oblong, 4-10-flowered, 4-6 mm. long; scales 

 brown with lighter margins and midrib, lanceolate, acuminate: bristles 2^6, 

 hispid, as long as the achene or longer: stamens 3: style 3-cleft: achene obovoid- 

 oblong, gray, rather abruptly beaked, its surface finely reticulated. Extends 

 across the continent; occasionally in our range, especially northward. 



