88 CYPERACEAE (SEDGE FAMILY) 



roots fibrous: culms tufted, very slender, 2-9 cm. high: spikelet ovoid, many- 

 flowered, subacute, 3-4 mm. long: scales minute, ovate-oblong, persistent, 

 purple-brown with green mid- vein: stamens 2-3: style 2-3-cleft: bristles 2-4, 

 fragile, white, minutely downwardly hispid, about as long as the achene: 

 achene jet black, shining, 0.5 mm. long, smooth, lenticular; tubercle conic, 

 minute. From Colorado to Nebraska and Iowa. 



4. Eleocharis oyata (Roth) R. & S. Syst. 2: 152. 1817. Culms nearly 

 terete, 1-3 dm. high: spikelets globose-ovoid to ovate-oblong, obtuse, 2-10 

 mm. long, dull brown: scales very obtuse, densely crowded in many ranks: 

 style 3-cleft: achene obovate, with narrow base, pale brown, shining, shorter 

 than the 6-8 bristles, broader than the short-deltoid acute and flattened 

 tubercle. Muddy shores; probably within the eastern part of our range. 



5. Eleocharis acicularis (L.) R. & S. 1. c. Stems with fibrous roots and very 

 slender running rootstocks, usually setaceous, 3-20 cm. high: spike 3-9- 

 flowered: scales acutish, more or less deeply tinged with brown: bristles 3 or 4, 

 often wanting: achene oblong-obovate, obscurely triangular and faintly ribbed 

 on the sides; tubercle broad, short and blunt, contracted at its junction with 

 the achene. On sandy or muddy stream banks across the continent. 



6. Eleocharis tenuis (Willd.) Schultes, Mant. 2: 92. 1824. Culms almost 

 capillary, erect from running rootstocks, 4-angular and flattish, the sides con- 

 cave : spikelet elliptical, acutish, 20-30-flowered : 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 one half as long as the achene or none. On our eastern 

 border and throughout the eastern half of the United States. 



7. Eleocharis rostellata Torr. Fl. N. Y. 2: 347. 1843. Culms flattened and 

 striate-grooved, wiry, erect, the sterile ones reclining, rooting and proliferous 

 from the apex, 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. Across the continent; infrequent in our range. 



4. ERIOPHORUM L. COTTON GRASS 



Perennials with creeping rootstocks and sometimes enlarged corm-like 

 bases. Stem (culm) leafy or often nearly naked. Spikelets single or clus- 

 tered, or umbellate, usually involucrate, with erect scale-like membranaceous 

 1-3-nerved bracts. Bristles naked, usually very numerous, often silky and 

 becoming greatly elongated. Style very slender and elongated. Achene 

 acutely triangular. 



Achene obovate; bristles more than 2 cm. long. 



Bracts oval or ovate, obtuse . . . . . . . .1. E. ocreatum. 



Bracts ovate-lanceolate . . . . . . . . 2. E. polystachyon. 



Achene linear-oblong; bristles less than 2 cm. long . . . . 3. E. gracile. 



1. Eriophorum ocreatum A. Nels. Bull. Torr. Bot. Club 29: 400. 1902. 

 Culms growing singly from the corm-like crowns of the short slender rhizomes, 

 finely striate, smooth, slender, 2-3 dm. high: sheaths 2-3, 2-3 cm. long, all 

 blade-bearing; blades broadly linear, rather rigid, short, 5-10 cm. long: leaves of 

 the involucre 2-4, the longer usually surpassing the inflorescence : spikelets 3-6, 

 subumbellate, the longer-peduncled ones drooping: scales oval or ovate, obtuse 

 or scarious-lacerate, brown: bristles numerous, glistening- white, 4-6 times as 

 long as the scales: achene broadly obovate, obtuse, dark brown. Cold, wet 

 subalpine parks; Wyoming and Colorado. 



2. Eriophorum polystachyon L. Sp. PI. 52. 1753. Stems stiff, smooth, 

 triangular above, nearly terete below, 3-8 dm. high, leafy: leaves flat, shorter 

 than the stem, tapering to a triangular rigid point: involucre of 2-4 leaves, 

 commonly equaling or exceeding the inflorescence: spikelets 3-12, ovoid or 

 oblong, nodding, in a terminal more or less compound umbel; rays filiform: 

 scales ovate-lanceolate, acute, or acuminate, purple-green or brown: bristles 



