CYPERACEAE (SEDGE FAMILY) 87 



the bristles. Borders of lakes and streams; from western Vermont to Illinois 

 and Wisconsin, and extending into our range at its northeastern border. 



10. Scirpus atrovirens Muhl. Gram. 43. 1817. Leaves somewhat more 

 rigid: spikelets dull greenish-brown, densely conglomerated (10-30 together) 

 into close heads, these also usually densely clustered in a less compound pani- 

 cle: 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; Colorado 

 and northward, and then across the continent. 



11. Scirpus microcarpus Presl. Rel. Haenk. 1: 105. 1828. Stem tall and 

 very leafy: the umbel-like or cymose panicle irregular, compound or decom- 

 pound: the longer leaf of the inflorescence exceeding the panicle: spikelets 

 ovoid-oblong, acute, 3-25 together in capitate clusters: scales brown with a 

 green midrib, obtuse or acute: bristles 4, barbed to the base: stamens 2: style 

 2-cleft: achene oblong-obovate, plano-convex, somewhat ridged on the back. 

 S. sylvaticus digynus. Frequent in our range and extending west to Cali- 

 fornia. 



12. Scirpus lineatus Michx. Fl. Bor. Am. 1: 32. 1803. Stem triangular, 

 leafy, 2-8 dm. high, leaves linear, flat: umbels terminal and sometimes axillary, 

 loose, drooping, the terminal with a 1-3-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, capillary, naked, not barbed, elongating, becoming tortuous and en- 

 tangled, much longer than the triangular achene. From New England to Wis- 

 consin and southward, coming into our range from western Kansas. 



3. ELEOCHARIS R. Br. SPIKE RUSH 



Stems tufted, from matted or creeping rootstocks, terete or angular, the 

 base covered with closely appressed sheaths: lower scale of the spikelet some- 

 times enlarged and bract-like. Scales closely imbricated all around the 

 rachis. Perianth of 3-9 short retrorsely barbed bristles, rarely none. Style 

 2-3-cleft, the conical or flattened tuberculate base persistent and mostly jointed 

 upon the summit of the turgid-triangular or lenticular achene. 



Style 2-cleft; achene lenticular. 



.Perennial by horizontal rootstocks. 



Yellowish-green, densely matted, 7-15 cm. high . . .I.E. thermalis. 



Bright green, matted, 2-10 dm. high . . . . .2. E. palustris. 



Annual, with fibrous roots. 



Achene black, with a minute tubercle . . . . . 3. E. atropurpurea. 



Achene brown, the ovoid tubercle one fourth as long as the achene 4. E. ovata. 

 Style 3-cleft; achene 3-angled or turgid. 



Achene reticulated; small tufted perennial . . . . . 5. E. acicularis. 

 Achene not reticulated; perennials 2-4 dm. high. 



Achene papillose . . . . . . . . . 6. E. tenuis. 



Achene smooth . . . . . . . . . . 7. E. rostellata. 



1. Eleocharis thermalis Rydb. Mem. N. Y. Bot. Gard. 1: 69. 1900. Peren- 

 nial from a slender creeping rootstock, mostly tufted and matted, yellowish 

 green: culms 3-10 cm. high, somewhat flattened, striate: upper sheath with a 

 hyaline limb: head obovate, obtuse, about 4 mm. long and 3 mm. in diameter, 

 light yellowish green; scales very thin, ovate, acutish: achenes lenticular, 

 broadly obovate, dark brown, smooth and shining, about 1 mm. long, about 

 four times as long as the conic acute tubercle. E. olivacea. Wyoming, Yel- 

 lowstone Park, Montana. 



2. Eleocharis palustris (L.) R. & S. Syst. 2: 151. 1817. Stems usually 

 slender, terete, striate, 2-10 dm. high: spike oblong-lanceolate to linear, acute, 

 10-25 mm. long: scales obtuse or the upper acutish, thin, brown with white 

 margin and greenish keel: bristles 4, about equaling the achene: achene 

 obovate, turgid, smooth; tubercle broad-deltoid, acutish or acute, rarely 

 acuminate. Throughout the continent, and in most parts of the Old World. 



3. Eleocharis atropurpurea (Retz.) Kunth. Enum. 2: 151. 1837, Annual, 



