50 CYPERACEAE. 



scales yellowish or rusty, strongly-nerved, scarious-margined, the green mid- 

 ribs ending in very short points; wing of the rachis narrow, not becoming di- 

 vided into scale-like parts. Banks of Snake River, rare. 



Cyperus strigosus L. Perennial from a globose tuber; stems erect, 10-50 

 cm. high; leaves flat, 4-6 mm. wide; umbel simple or compound, the longest 

 rays 8-12 cm. long, their sheaths terminating in 2 bristles; spikelets linear, 

 8-16 mm. long, 7-15-flowered; scales pale, oblong-lanceolate, appressed, 

 subacute; akene linear-oblong, acute. Sandy bars of Clearwater River. 



Cyperus houghtonii Torr. Perennial; stems 20-60 cm. high, much exceed- 

 ing the leaves; leaves narrow, 1-2 mm. wide; involucral leaves about as long 

 as the inflorescence; umbel with 1-5 unequal rays, some nearly sessile, a few 

 elongate; spikelets in loose heads, oblong-linear, 8-14 mm. long, 11-15- 

 flowered; scales brownish, mucronate, strongly nerved, exceeding the brown 

 akene. Along the Clearwater River near Lewiston, Idaho. 



67. ELEOCHARIS. SPIKE RUSH. 



Annual or perennial; stems simple, triangular, quadrangular, 

 terete, flattened or grooved, the leaves reduced to sheaths or the 

 lowest very rarely blade-bearing; spikelets solitary, terminal, 

 erect, several-many-flowered, not subtended by an involucre; 

 scales concave, in a spiral; perianth of 1-12 bristles usually 

 barbed ; stamens 2 or 3 ; akene 3-angled or biconvex ; base of the 

 style persistent on the summit of the akene forming a terminal 

 tubercle. 



Akenes 3-angled; spikelets few-flowered. E. acicularis. 

 Akenes biconvex; spikelets many-flowered. 



Plants not tufted; perennial with running rootstocks. E. palustris. 

 Plants tufted, annual. 



Heads ovoid ; bristles longer than the akenes. E. obtusa. 



Heads oblong; bristles not longer than the akenes. E. monticola. 



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. Very abundant 

 in wet places. 



Eleocharis acicularis bella Piper. Rootstocks very short, so that the plant 

 forms dense round tufts 5-10 cm. in diameter; stems ascending or spreading, 

 only 2-5 cm. long; otherwise as in the species. Rare on muddy banks of 

 streams. In habit very different from E. acicularis, but lacking good mor- 

 phological characters. In marked contrast to the species, the subspecies 

 produces akenes freely. 



Eleocharis palustris (L.) Roem. & Schult. Rootstocks extensively creeping; 

 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 at the edges of ponds 

 or in shallow water. 



Eleocharis obtusa Schult. Stems erect or ascending, densely tufted, 

 5 to 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 muddy places, uncommon. 



