180 



CYPERACEAE (SEDGE FAMILY^ 



Strictly l-flowered ; upper scales ovate, pointed, rough on the keel ; stamens and 

 styles 2 ; leaves linear. — Low grounds, Md. to O., 111., and southw. Aug.-Oct. 

 Fig. 236. 



3. DULfCHIUM Pers. 



Spikelets linear, flattened, sessile in 2 ranks on peduncles 

 emerging from the sheaths of the leaves ; scales lanceolate, 

 decurrent, forming flat wing-like margins on the joint below. 

 Perianth of 6-9 downwardly barbed bristles. Stamens 3. 

 Style 2-cleft above. Achene flattened, linear-oblong, beaked 

 with the long persistent style. — A perennial herb, with " 

 terete simple hollow culm (2-10 dm. high), jointed and 

 leafy to the summit ; leaves short and flat, linear, 3-ranked. 

 (Name of uncertain origin.) 



1. D. arundinaceum (L.) Britton. (i>. spathaceum 

 Pers.) — Wet swamps and borders of ponds, Nfd. to Wash., 

 and southw. July-Oct. Fig. 237. 



D. arundinaceam. 



4. ELE6CHARIS R. Br. Spike Rush 



Spikelet few-many-flowered. Scales imbricated in many (rarely in 2 or 

 3) ranks. Perianth of 3-12 (commonly 6) bristles, usually rough or barbed 

 downward, rarely obsolete. Style 2-3-cleft, its bulbous base persistent as a 

 tubercle jointed upon the apex of the lenticular or triangular achene. — Leafless 

 (rarely with basal capillary leaves), chiefly perennial, with tufted culms sheathed 

 at the base, from matted or creeping rootstocks ; flowering in summer. (Name 

 from ^\os, a marsh, and x^/"^) grace; being marsh plants.) 



a. Spikelet hardly If at all thicker than the spongy-cellular culm ; scales 

 firmly persistent. 

 Spikelet cylindric, many-flowered ; scales coriaceous, faintly nerved 

 or nerveless. 



Culm terete 1, E. interatincia. 



Culm sharply i-angled 2. E, guadrangulata. 



Spikelet linear- or lance-awl-shaped, few-flowered ; scales herba- 

 ceous, distinctly nerved 8, E. Mobhinsii. 



lb. Spikelet much thicker than the culm (or, if slender, with deciduous 

 scales) b. 

 ft. Achenes lenticular or biconvex^ styles mostly 2-cleft c. 

 0. Upper sheaths loose, with white scarious tips. 



Scales white, with green midribs 4. ^. ochreata. 



Scales purple-brown, with green midribs 5. JT. oUvacea. 



e. Upper sheaths close and Arm, green, not scarious, the tips often 

 dark-margined d. 

 d. Plants tufted, mostly annual, without conspicuous rootstocks e. 

 e. Mature achenes black ; tubercle saucer-shaped ; upper sheath 

 oblique at tip, the elongate tooth narrow-deltoid. 

 Spikelet 1.5-2 mm. thick; achene 0.5 mm. long . . . 6. E. airopurpitrea, 

 Spikelet 2.5-3 mm. thick; achene 1 ram. long. 

 Scales whitish-brown, with greenish rib ; achenes jet 



black 1. E. capiiata. 



Scales purple-brown ; achenes purple-black . . (7) E. capiiata, v. dispar. 

 e. Mature achenes whitish to pale brown ; tubercle conic or 

 deltoid ; upper sheath with nearly truncate tip, the 

 short tooth broad-deltoid / 

 ■ /. Tubercle less than two-thirds as broad as the achene. 



Tubercle depressed turban-shape, broader than high ; 



bristles wanting or rudimentary . . . . S. E. diandra,^ 

 Tubercle deltoid-conic, higher than broad ; biistles 



much exceeding the achene 9. E. ovata. 



/. Tubercle nearly or quite as broad as the achene. 



Tubercle.depressod-conic, concaved toward the tip, one- 

 third as high as the achene ; bristles much exceeding 



the achene 10. ^. oMuea. 



Tubercle flat-deltoid, with straight sides, one-fourth as 

 hiffh as the achene , bristles scarcely or not at all ex- 

 ceeding the achene. 

 Bristles about equaling the achene . . .11. E. Engtilmanni. 



Bristles rudimentary or wanting . . (11) E. Eiigelmanni, v, detonea. 

 d. Plants not tufted, perennial from elongate rootstocks . . 12. E. palustris. 



