3 I2 SYSTEMATIC BOTANY. 



1. E. OBTUSA (Spike Rush}. Culms nearly terete in tufts ; spike globose v 

 at length becoming somewhat cylindrical, obtuse, densely many-flowered ; 

 glumes very obtuse, light brown, whitish on the margin ; achenium obovate, 

 of a shining brown, surrounded by 6 bristles. In shallow water and muddy 

 grounds, 6'-i2 ( high. July-August. 



2. E. PALUSTRIS (Round Rush}. Culm nearly terete ; spike oblong- 

 lanceolate, acute, many-flowered, often obliquely attached ; glumes reddish- 

 brown, achenium obovate, surrounded by about four bristles longer than it- 

 self, and crowned with a small, ovate, flattened tubercle. In shallow water 

 and low grounds, 6'-2o' high. June-July. 



3. E. TENUIS (Slender Rush). Culm very slender and wiry, 4-angled 

 with concave sides ; spike elliptical, 2o-3o-flowered ; glumes ovate, obtuse ; 

 achenium obovate, with a small, depressed tubercle, and surrounded by 

 bristles. In wet meadows, 6'-i2' high. June-July. 



4. Scirpus. Spikes cylindrical, clustered. Glumes imbricated in 

 no order. Perianth of 3-6 bristles. Stamens 3. Style 2-3-cleft. 

 Culms sheathed at base. 



1. S. VALIDUS (Bulrush)'. Culm tall, cylindric, filled with spongy 

 pith, tapering above, dark green ; spikes oblong-ovate, numerous, arranged 

 in a compound panicle ; glumes ovate, achenium obovate, mucronate, sur- 

 rounded by 4-5 bristles. In wet grounds, 4-8 feet high. July. 



2. S. PUNGENS (Acute Club Rush). Culm acutely angled with concave 

 sides ; leaves few below, channeled above, often 6'-8' long ; spikes ovoid, 

 sessile, 1-5 in a cluster ; glumes ovate, 2-cleft, mucronate ; style 2-cleft ; 

 bristles 2-6, shorter than the obovate, mucronate achenium. In ponds and 

 streams. July-August. 



3. S. ATROVIRENS (Umbelled Club Rush). Culm obtusely triangular, 

 rigidly erect, leafy ; leaves broad-linear, rough on the margin, flat ; spike 

 ovoid, crowded in dens3, globular, dark, dull-green heads, containing icn-2o 

 spikes. July. 



5. Eriophorum. Spikes many-flowered. Scales imbricated all 

 round without order. Perianth consisting of numerous, rarely 6, 

 woolly, persistent bristles. Stamens mostly 3. Style 3-cleft. 



1. E. POLYSTACHYON (Cotton Grass). Culm rigidly erect, obscurely 3- 

 angled ; leaves linear, flat, terminating in a triangular point ; involucre 2-3- 

 leaved ; spikes about 10, on slender, nodding peduncles. Wool straight, 

 nearly an inch long. Bogs and meadows, 1-2 feet high. June. 



2. E. VIRGINICUM (Brown Cotton Grass). Culm rather stout, rigid, 

 nearly terete, leafy ; leaves long, flat, narrowly-linear, rough on the margin ; 

 involucre 2-4-leaved ; spikes erect, crowded in a dense head ; wool dense, of 

 a rusty-brown color, 3 or 4 times as long as the scale ; stamen i. July- 

 August. 



6. Fimbristylis. Spike several or many-flowered. Glumes im- 

 bricated in regular rows. Perianth of bristles none. Stamens 1-3. 



