Scirpus. CYPERACJLE. 217 



the spikelets in a terminal (or apparently lateral) involucrate cluster or compound 

 umbel-like panicle, or solitary. 

 A cosmopolitan genus of nearly 250 species, of which about 30 are found in the United States. 



1. Spikelet solitary, small, with a single erect involucral bract : bristles none : 

 stems low and slender. ISOLEPIS, Benth. 



1. S. riparius, Spreng. Stems tufted, from fibrous roots, very slender and often 

 setaceous, 2 to 6 or rarely 10 inches high, sheathed at base, the upper sheath usually 

 bearing a short slender leaf : involucral bract 1 to 10 lines long or nearly wanting : 

 spikelet ovate to oblong-ovate, 1| to 2J lines long : scales pale or often deep brown, 

 with a pale prominent midvein, concave, obtuse or pointed : stamens usually 3 : 

 style 3-cleft : nutlet triangular-obovoid with distinct angles, the sides convex, smooth 

 or minutely granular, not striate nor ribbed, dark brown when mature, less than half 

 a line long. Benth. Fl. Austr. vii. 327. Isolef>is riparia, R. Br. ; Hook. f. Fl. 

 Tasrn. ii. 89, t. 145. S. Savii, Reichenb. Icon. Fl. Germ, viii, t. 301. Isolepis 

 leptocaulis, Torr. Pacif. R. Rep. iv. 153. S. pygmcem, Gray, Proc. Amer. Acad. vii. 

 392. S. setaceus, Linn., var., Boeckeler, Linnaea, xxxvi. 500. 



Frequent in marshy places near the coast from Santa Barbara to Oregon ; also in South America, 

 Australia, Africa and the Mediterranean region. 



2. S. carinatus, Gray, 1. c. Resembling the last in habit, the slender stems 

 triangular and channelled, 1 to 4 inches high, with a short leaf at base : spikelet 

 (rarely 2 or 3) greenish or tinged with brown, 5 - 10-flowered ; scales in 4 ranks, 

 very broadly ovate, strongly carinate and boat-shaped, acute, gibbous in fruit and 

 retaining the brown nutlet, which is very broad, acutely triangular, smooth, over 

 half a line long, with a broad scar at the summit. Boeck. 1. c. 498. Isolepis cari- 

 nata, Hook. & Arn. ; Torr. Gyp. 349. /. koilolepis, Steud. Cyp. 318. 



In swamps about San Francisco, abundant with the last (Bol cinder); Santa Rosa Creek (Bigc- 

 low); Mendocino County (Bolander); in the Gulf States, from Alabama to Arkansas and Texas. 



2. Bristles present, retrorsely barbed or ciliate, not elongated : stems mostly 

 tall and stout. EUSCIRPUS, Benth. 



* Inflorescence apparently lateral, with a single erect involucral leaf. 



f Stem terete ar nearly so. 

 H- Stem leafy at base : spikelets in a sessile cluster. 



3. S. Nevadensis, Watson. Stems clustered, from a running rootstock, a foot 

 or two high, very slender, somewhat flattened above : leaves nearly equalling the 

 stem, deeply channelled or revolute, very rough on the margins, sharply acute : 

 spikelets 1 to 8, ovate-oblong, acute, 4 to 10 lines long ; scales brown and shining, 

 ovate, slightly carinate, acutish : bristles 1 to 3, not half the length of the nutlet : 

 style 2-cleft : nutlet broadly ovate, plano-convex, acute, a line long. Bot. King 

 Exp. 360. 



Borders of Mono Lake, on alkaline soil (Brewer, n. 1846); at Soda Lake, Nevada, Watson. 



H- -H- Stem leafless or nearly so : spikelets umbelled. 



4. S. lacustris, Linn. Stem stout and tall, from creeping rootstocks, terete or 

 very obtusely triquetrous above, leafless or the upper basal sheaths with a short 

 terete leaf: involucral bract stout, shorter than the inflorescence : spikelets numerous, 

 solitary or more or less clustered, in an irregularly compound umbel, oblong-ovoid, 

 3 to 6 lines long ; scales broadly ovate, very obtuse or usually emarginate and mucro- 

 nate, ciliate : bristles usually 6, slender with scattered barbs, about equalling the 

 obovate plano-convex nutlet : style usually 2-cleft. Reichenb. 1. c., t. 306 - 308 ; 

 Boeck. 1. c. 712 ; Benth. 1. c. 333. S. validus, Vahl. 



