CYPERACEAE. 83 



Styles 2-cleft; akenes biconvex. 



Tubercles constricted basally; perennial with rootstocks. E. palustris. 



Tubercles not constricted basally; annual, tufted. E. obtusa. 

 Styles 3-cleft; akenes 3-angled. 



Tubercles broad and short; akenes ribbed. E. acicularis. 



Tubercles subulate; akenes smooth. E. rostellata. 



Eleocharis palustris (L.) Roem. & Schult. Rootstocks extensively creep- 

 ing; stems 30-70 cm. tall; spike lanceolate-oblong, 1-2 cm. long; bristles 4, 

 usually exceeding the obovate smooth biconvex akene; tubercle obtuse, 

 contracted at its junction with the akene; style 2-cleft. 



Abundant in wet ground and in shallow water. 



Eleocharis obtusa (Willd.) Schult. Stems erect or ascending, densely tuft- 

 ed, 5-7 cm. high; spikelets brownish, ovoid, obtuse, 2-13 mm. long; bristles 

 6-8, exceeding the brown shining akene; tubercle very short and broad, deltoid, 

 acute. 



In wet places, quite common. 



Eleocharis acicularis (L.) Roem. & Schult. Perennial by creeping root- 

 stocks, usually forming extensive mats; stems very slender, 7-15 cm. tall, 

 erect; spikes 3-10-flowered, 3-5 mm. long; bristles 3 or 4, shorter than the 

 akene or wanting; akene oblong or obovoid, somewhat 3-angled, marked with 

 9-12 longitudinal ribs, with very numerous cross-lines between them; tubercle 

 broad, contracted at its junction with the akene; style 3-cleft. 



Abundant on the margins of ponds often forming a sward. 



Eleocharis rostellata Torr. Perennial, the sterile shoots decumbent and 

 rooting at the tips; fertile erect, wiry, 30-60 cm. high; spikelets fusiform, 

 12-20-flowered; bristles longer than the akenes. 



In marshes, rare. Vancouver Island, Macoun; Skamania County, Suksdorf. 



99. SCIRPUS. 



Annual or perennial ; stems leafy or the leaves reduced to basal 

 sheaths; spikelets terete (in ours), solitary, or in a terminal 

 cluster which is subtended by a 1 -several-leaved involucre; 

 scales in a spiral, usually all fertile, one or two of the lowest 

 sometimes empty; flowers perfect; perianth of 1-6 bristles, or 

 sometimes none ; stamens 2 or 3 ; style 2 or 3-cleft, not swollen at 

 the base ; akene triangular, lenticular or plano-convex. 



Spikelets solitary, terminal. 



Involucral bract wanting. S. nanus. 



Involucral bract present. 



Bract 2-3 times as long as the spikelet. 5. subterminalis. 



Bract not longer than the spikelet. 



Perianth bristles none. 5. riparius. 



Perianth bristles 6, smooth. S. cespitosus. 



Spikelets several-many, rarely solitary. 

 Stems terete; inflorescence umbellate. 



Akenes 2.5-3 mm. long, the scales one-fourth longer. S. occidentalis. 

 Akenes 2 mm. long, the scales little longer. S. validus. 



Stems three-angled. 



Involucral leaf solitary. S. americanus. 



Involucral leaves several. 



Spikelets 1-2 cm. long. S. robustus. 



Spikelets 3-5 mm. long. 5. microcarpus. 



