crPEKACE^. (sedge family.) 493 



10. C. acnminiktns, Torr. Slender (3' -12' high); fipikes ovate, iecom- 

 ing oblong, 16-30-flowercd, pale, collected in simple or compound heads; scales 

 olisairelii 3-neived, their short acute tips somewhat spreading; achenium oblong, 

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



* * * Root perennial : stamen only 1 : spikes short and flat, ovate and oblong, ciowd- 

 ed in dose globular heads ; the joints qf the axis not margined. 



11. C. vireilS, Michx. Culm (l°-4°high) either sharply or obtusely 

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

 rayed ; aehenium oblong or linear, J to | the length of the nan-ow oblong acut- 

 iah scale. ( C. vegetus, Torr.) — Wet places, Virginia and southward. — Heads 

 of spikes green, turning tawny. 



* * # * Root perennial : rootstocks creeping, or tuberous : stamens 3. 



•>- Spikes flat, dosdy flowered, ovate-oblong or becoming broadly linear, 3-5 at the 



end of each ray of the compound umbel. 



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

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

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

 obovate, shai-ply triangular. — Sandy swamps, Massachusetts to Virginia, and 

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

 *- -1- Spikes flat, closely flourered, linear (^' - 1' long), loosely spiked along tlie upper 



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

 bearing small nut-lilce tvhers. 



13. C. rotundus, L., var. H^dra. (Nut-Gkass.) >Calm slender 

 (^°-l^° high), longer than the leaves; umbel simple or slightly compound, 

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

 purple 12-40-flowered acute spikes; scales ovate, closely appressed, 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. phyinatodes, Mnhl. Culm (1°-Jj° high) equalling the leaves; 

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

 numet'ons, light chestnut or straw-color, acatish, 12- 30-flowered; scales oblong, nar- 

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

 (C. repens. Ell.) — Low grounds, along rivers, &o., 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. 



^- H- H— Spikes flattish, rather loosely flowered, greenish, lance-linear, capitate-clus- 

 tered {except \n No. 15); the convex ovate scales many-nerved, only J or .-J longer 

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



15. C ScIl'WeinitZU, Torr. Culm rough on the angles (1°- 2° high) ; 



leaves linear; umbel simple, 4-8-rayed; spikes crowded at the upper part of the 



mostly elongated rays, erect, loosely 6 - 9-flowered, a bristly bract at the base of 



each ; scales awl-pointed, scarcely longer than the ovate aehenium ; joints of the 



axis narrowly winged. — Dry sandy shores, &c.. Lake Ontario, New York, to 



Illinois, and northwestward. Aug. — Spikes i'-^' long: the scales largo in 



proportion. 



42 



