368 CYPERACE^. (SEDGE FAMILY.) 



Var. digynus, Boeck. Stijle 2-cIeJl, akene not at all angled on the back 

 stamens 2, and bristles 4. — *S. microcarpus, Presl, of Gray's Manual. From 

 California to Colorado and across the continent northward. The type is 

 rarely collected in New England. 



8. S. atrovirens, INIuhl. Very similar to the last: panicle more con- 

 tracted, the smaller spikelets crowded in denser and larger clusters: scales 

 narrower and narrowlij acuminate: bristles scarcely barbed below the middle: 

 style 3-cleft: akene oblong-obovate, more acuminate, slightly angled on the bach 

 — In Avet meadows and bogs from Colorado to California and Oregon, and 

 eastward to New England. 



* * Bristles capillary, naked, not barbed, elongating, becoming tortuous and 

 entangled, much longer than the triangular akene. 



9. S. lineatUS, Michx. Stem triangular, leafy, 1 to 3 feet high : leaves 

 linear, flat : umbels terminal and sometimes axillary, loose, drooping, the 

 terminal with a 1 to 3-leaved involucre much shorter than the long slender 

 rays : spikes oblong, becoming cylindrical, on filiform drooping pedicels : 

 bristles at maturity scarcely exceeding the green-keeled and pointed scales : 

 akene sharp- pointed. — From New England to Wisconsin and southward, 

 coming into our range from W. Kansas. 



3. ERIOPHORUM, L. Cottox-Grass. 



Distinguished from Scirpus chiefly by very numerous naked silky bristles 

 which become loug-exserted in fruit. Style very slender and elongated 

 3-cleft. Akene acutely triangular. — Perennials with creeping rootstocks. 



1. E. gracile, Koch. Stem very slender, 1 or 2 feet high : leaves slender, 

 channelled-triancpdar : involucre of I to 3 brownish scales : spikelets 2 to 5 on 

 short tomentose-scabrous slightly nodding rays : akene linear-oblong, broadest 

 above. — Cold bogs across the continent in the northern tier of States. 



2. E. polystachyum, L. Stouter : leaves linear, flat or barely chan- 

 nelled below : involucre more conspicuous, 2 or 3-leaved : spikelets more numerous 

 and larger, upon longer nodding usually smooth rays : akene broader, obovate. — 

 From Colorado northward, and thence eastward across the continent ; also in 

 Oregon. 



4. HEMICARPHA, Nees. 



Distinguished from Scirpus chiefly by the minute hyaline bractlet between 

 the flower and the axis. Style 2-cleft. — Low setaceous annuals, with flattened 

 stems, somewhat leafy at base. 



1. H. subsquarrosa, Nees. Stems numerous, tufted, 1 to 6 inches high, 

 browu-sheathed at base, with 1 or 2 very short filiform leaves : principal invo- 

 lucral bract continuous with the stem, the others much smaller or none r 

 scales brown, tipped with a short recurved point. — From California to New 

 Mexico and Colorado and eastward through the Atlantic States. 



5. ELEOCHARIS, R.Brown. Spike-Rush. 



Scales closely imbricated all around the rhachis. Perianth of 3 to 9 shorv 

 retrorsely barbed bristles, rarely none. Style usually 3-cleft, the conical or 



