180 



CYPERACEAE (SEDGE FAMILY) 



strictly 1 -flowered ; upper scales ovate, pointed, rough on the keel ; stamens and 

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

 FIG. 236. 



3. DULiCHIUM 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 a 

 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. (D. spathaceum 

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

 7. D. arundinaceum. and SOUthw. July-Get. FlG. 237. 



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 IXoj, a marsh, and x&P 1 *, grace; being marsh plants.) 



4. E. ochreata. 



5. E. 



6. E. atropurpurea. 



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. inter stincta. 



Culm sharply 4-angIed ......... 2. E. quadrangulata. 



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



ceous, distinctly nerved ........ 3. E. Sobbinrii. 



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



scales) b. 



b. Achenes lenticular or biconvex ; styles mostly 2-cleft c. 

 c. Upper sheaths loose, with white scarious tips. 



Scales white, with green midribs ....... 



Scales purple-brown, with green midribs ..... 



c. Upper sheaths close and firm, green, not scarions, the tips often 



dark-margined d. 



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

 . 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 . . 

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

 Scales whitish-brown, with greenish rib ; achenes jet 



black .......... 7. E. cupitata. 



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

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

 deltoid ; upper sheath with nearly truncate tip, the 

 short tooth broad-deltoid f. 



f. Tubercle less than two-thirds as broad as the achene. 

 Tubercle depressed turban-shape, broader than high ; 



bristles wanting or rudimentary . . . 

 Tubercle deltoid-conic, higher than broad ; bristles 

 much exceeding the achene ..... 



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



Tubercle dep'ressed-conic, concaved toward the tip, one- 

 third as high as the achene ; bristles much exceeding 

 the acbene ......... 10. E. obtusa. 



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

 hi?h as the achene ; bristles scarcely or not at all ex- 

 ceeding the achene. 



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

 Bristles rudimentary or wanting . . (11) E. Engetmanni, v. dttonta. 

 tl. Plants not tufted, perennial from elongate rootstocks . . IX E. palinstris. 



8. E. diandra. 



9. E. ovaia. 



