CYPERACF^E. (SEDGE FAMILY.) 493 



10. C. nctimimstllS, Torr. Slender (3' -12' high) ; spikes ovate, becom- 

 ing oblong, lG-30-flowered, pale, collected in simple or compound heads; scales 

 obscurely 3-nerced, their short acute tips someichat spreading ; aehenium oblong, 

 pointed at both ends. Low ground, Illinois and westward. 



* = #- Root perennial : stamen only 1 : spikes short and flat, ovate and oblong, crowd- 

 ed in close globular heads ; the joints of the axis not margined. 



11. C. VireaiS, Miehx. Culm (1- 4 high) either sharply or obtusely 

 triangular; leaves and involucre very long, keeled; umbel compound, many- 

 rayed ; aehenium oblong or linear, ^ to | the length of the narrow oblong acut- 

 ish scale. (C. vcgetus, Torr.} Wet places, Virginia and southward. Heads 

 of spikes green, turning tawny. 



* * w * Root perennial : root stocks creeping, or tuberous: stamens 3. 



-t- Spikes flat, closely flowered, ovate-oblong or becoming broadly linear, 3-5 at the 



end of each ray of the compound umbel. 



12. C. clentsUus, Torr. Culm slender (6' -12' high) ; umbel 4-7-rayed; 

 spikes 6 - 30-flowered ; scales strongly keeled, and with abruptly sharp-pointed 

 slightly spreading tips, reddish-brown on the sides, green on the back ; aehenium 

 obovate, sharply triangular. Sandy swamps, Massachusetts to Virginia, and 

 southward. Aug Spikes 2"- 5" long, sometimes changing into leafy tufts. 

 *- *- Spikes flat, closely flowered, linear (^ - 1' long), loosely spiked along the upj>er 



part of the rays of the open umbel: rootstocks slender, creeping extensively, and 

 bearing small nut-like tubers. 



13. C. rotutidus, L., var. Hydra. (NUT-GRASS.) Culm slender 

 (- 1-g- high), longer than the leaves; umbel simple or slightly compound, 

 about equalling the involucre; the few rays each bearing 4 - 9 dark chestnut- 

 purple 1 2 - 40-flowercd acute spikes ; scales ovate, close!// oppressed, nerveless except 

 on the green keel. (C. Hydra, Michx.) Sandy fields, Virginia and south- 

 ward : probably an immigrant from farther south. Excessively troublesome to 

 planters. (Eu.) 



14. C. phyeieatodCS, Muhl. Culm (1- 2^ high) equalling the leaves; 

 umbel often compound, 4- 7 -rayed, much shorter than the long involucre ; spikes 

 numerous, light chestnut or straw-color, acutish, 12-30-flowercd ; scales oblong, nar- 

 rowly scarious-margincd, nerved, the acutish tips rather loose ; aehenium oblong. 

 (C. repens, Ell.} Low grounds, along rivers, &c., Vermont to Michigan, Illi- 

 nois, and common southward. Aug. Tubers small, at the end of very slender 

 rootstocks : by these the plant multiplies rapidly, and becomes a pest. 

 *-*-- Spikes flattish, rather loosely floivered, greenish, lance-linear, capitate-clus- 

 tered (except in No. 15) ; the convex ovate scales many-nerved, only or 4- longer 

 than the triangular aehenium: culms tufted from hard tuberiferous rootstocks. 



15. C. ScllWC'illUzii, Torr. Culm rough on the angles (1- 2 high) ; 

 leaves linear; umbel simple, 4-8-rai/ed; fpikes crowded at the upper part of the 

 mostly elongated ray,-:, erect, loosely 6 - 9-flowcrcd, a bristly bract at the base of 

 each ; scales a u:l -pointed, scarcely longer than the ovate aehenium ;. joints of the 

 axi* narrowly winged. Dry sandy shores, &c., Lake Ontario, New York, to 

 Illinois, and northwestward. Aug. Spikes y -# long: the scales large ill 

 proportion. 



