MACLOSKIE I CYPERACE^E. 263 



10. S. RIPARIUS Presl. 



Culm obtusely trigonal, finely striate. Involucre 2-leaved, the outer 

 leaf straight, pungent, continuing the culm, shorter than the umbel, the 

 inner leaf still shorter. Umbel many-rayed, its rays trigonal. Bracts 

 lanceolate, i -nerved. Spikes ovate-oblong, many-flowered. Scales ellip- 

 tical-round, i-nerved, emarginate-mucronulate. Setce 2, retrorsely scabrid. 

 Style bifid. Achene obovate, plano-convex. 



(Calif, to Chili); N. Fuegia, rare, Dusen ; abundant on the banks of 

 Lago Nahuel-huapi. 



S. RIPARIUS TERETICULMIS Steud. 



Approaching S. americanus by its more or less terete, flavescent culms, 

 25-75 cm. high, finely striate, its depauperate umbel, about 6-rayed, its 

 sanguineous bracts, its smaller dark sanguineous spikes, its broad-ovate, 

 long-avvned scales. Style long, bifid. 



S. Patagon., by banks of Pa von I., in Rio Sta. Cruz, and Lago Argen- 

 tine. 



ii. S. SETACEUS Linn. p. p. 



Ciilms cespitose, filiform, i -leaved at base, glabrous; the leaf linear- 

 filiform, shorter than the culm. Spikes solitary or in pairs, rarely 3 or 4, 

 ovate, obtuse, few-flowered. Involucre of i leaf, exceeding the spikes. 

 Scales ovafe, submucronate, green at the keel, hyaline-white with a purple 

 spot at each side. Achene round-elliptical mucronate, its sides ribbed 

 lengthwise and striate across. 



(Eurasia, Austral., Chili); Magellan. 



4. HELEOCHARIS (Eleocharis] R. Br. Spike-rush. 



Sedges with simple culms, the leaves usually reduced to sheaths. 

 Spikelet solitary, terminal, erect, many-flowered, not involucrate. Scales 

 concave, imbricated spirally. Perianth-bristles 1-8, retrorsely barbed, or 

 none. Stamens 2-3. Style 2-3-cleft, its base enlarged and persisting as 

 a rostrum on the lenticular or trigonal achene. 



Species 80, cosmopolitan, from tropics to the arctic regions. 



KEY TO THE SPECIES. 

 a. Style usually 2-cleft. 



b. Low, creeping by thick rootstock. Stylo-base constricted. Setae none-3. funebris. 

 b2. Creeping horizontally ; stout. Achene with flat rostrum. Setae 4 or none, palustris. 



