248 



CYPERACEAE. 



4. ELEOCHARIS R. Br. Prodr. Fl. Nov. Holl. i: 224. 1810. 

 Annual or perennial sedges. Culms 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 con- 

 cave, spirally imbricated all around. Perianth of 1-12 bristles, usually retrorsely barbed, 

 wanting in some species. Stamens 2-3. Style 2-cleft and achene lenticular or biconvex, or 

 3-cleft and achene 3-angled, but sometimes with very obtuse angles and appearing turgid. 

 Base of the style persistent on the summit of the achene, forming a terminal tubercle. 

 [Greek, referring to the growth of most of the species in marshy ground.] 



About 100 species, widely distributed. Besides the following, some 15 others occur in the 

 southern and western parts of North America. 

 Spikelet scarcelj' or not at all thicker than the culm. 

 Culm stout; spikelet many-flowered. 



Culm terete, nodose. i. E. interstincla. 



Culm quadrangular, continuous. 2. E. mutata. 



Culm slender, triangular, continuous; spikelet few-flowered, subulate. 3. E. Robbinsii. 

 Spikelet manifestly thicker than the culm. 



Style mostly 2-cleft; achene lenticular or biconvex. 



Upper sheath scarious, hyaline ; plants perennial by slender rootstocks. 



Scales pale green or nearly white; achene K" long. 

 Scales dark reddish-brown ; achene %" long. 

 Upper sheath truncate, oblique or toothed, not scarious. 

 Annual, with fibrous roots. 

 Achene jet black. 



Culms i '-3' tall; achene K" long; bristles 2-4. 

 Culms 3'-io' tall; achene 1 A" long; bristles 5-8. 

 Achene pale brown. 



Spikelet ovoid or oblong; tubercle deltoid, acute. 

 Spikelet pblong-cylindric; tubercle broad, low. 

 Perennial by horizontal rootstocks. 

 Style 3-cleft; achene 3-angled or turgid. 

 Achene reticulated or cancellate. 



Spikelet compressed; culm filiform. 

 Spikelet terete ; culm slender. 



Achene transversely cancellate; bristles none. 

 Achene reticulated ; bristles present, stout. 

 Tubercle conic, smaller than the achene. 

 Tubercle cap-like, as large as or larger than the achene. 

 Achene smooth or papillose. 



Achene smo_oth, white ; culms capillary. 

 Achene papillose or smooth, brown, black or yellow. 

 Tubercle depressed or short-conic. 

 Achene smooth. 



Tubercle flat, covering the top of the black achene. 

 Tubercle ovoid-conic, acute, contracted at the base. 

 Achene papillose. 



Achene 3-ribbed on the angles. 

 Achene obtuse-angled, not ribbed. 

 Culm filiform; scales obtuse. 

 Culm flat; scales acute. 

 Tubercle subulate or narrowly pyramidal. 



Culms filiform, wiry, densely tufted, 4'-io' long. 

 Culms flattened, slender, i-2 long. 



4. E. ochreata. 



5. E. olivacea. 



E. atropurpurea. 

 E. capilata. 



E. ovata. 



E. Engelmanni. 



E. palustris. 



11. E. acicularis. 



12. E. Wolfii. 



13. E. tortilis. 



14. E. tuberculosa. 



15. E. microcarpa. 



1 6. E. melanocarpa. 



17. E. albida. 



18. E. tricostata. 



19. E. tennis. 



20. E. acuminata. 



21. E. intermedia. 



22. E. rostellata. 



i. Eleocharis interstincta (Vahl) R. &S. Knotted Spike-rush. (Fig. 577.) 



Scirpus interstinctus Vahl, Enum. 2: 251. 1806. 

 Scirpus equisetoides Ell. Bot. S. C. & Ga. i: 79. 1816. 

 Eleocharis interslincta R. & S. Syst. 2: 148. 1817. 

 Eleocharis equisetoides Torr. Ann Lye. 3: 296. 1836. 



Perennial by stout rootstooks, culms terete, hol- 

 low, nodose, papillose, i^-3 tall, the sterile ones 

 sharp-pointed. Sheaths oblique, membranous, 

 brown or green, the lower sometimes bearing short 

 blades; spikelet terete, cylindric, many-flowered, 

 subacute, I'-ity long, 2" in diameter, not thicker 

 than the culm; scales ovate, orbicular or obovate, 

 obtuse or the upper acute, narrowly scarious-mar- 

 gined, faintly many-nerved, persistent; bristles 

 about 6, rigid, retrorsely barbed, as long as the body 

 of the achene or shorter; stamens 3; style 3-cleft, 

 exserted; achene obovoid, brown, shining, with 

 minute transverse ridges, convex on one side} very 

 obtusely angled on the other, 2 or 3 times as long 

 as the conic acute black broad-based tubercle. 

 In water, Massachusetts to Michigan, the West Indies and Mexico. July-Sept. 



