CYPERACE^E. ^SEDGE FAMILY.) 493 



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

 ing oblong, 1 6 - 30-flowered, pale, collected in simple or compound heads ; scales 

 obscurely 3-nerved, their short acute tips somewhat spreading ; achcnium oblong, 

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



* * * Root perennial: stamen only 1 : spikes short and fiat, ovate and oblong, crowd- 

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



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

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

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

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

 of spikes green, turning tawny. 



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



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



end of each ray of the compound umbel. 



12. C. dClltatllS, 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 ; achenium 

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

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

 +~ H Spikes fiat, closely flowered, linear (j 1 - 1' long), loosely spiked along the upper 



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

 bearing small nut-like tubers. 



13. C. rotimdus, L., var. Hydra. (NUT-GRASS.) Culm 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 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. ptiymatodes, 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-flowered; scales oblong, nar- 

 rowly scariovs-margined, nerved, the acutish tips rather loose; achenium 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. 



- H -*- Spikes flatfish, rather loosely flowered, greenish, lance-linear, capitate-clus- 

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

 than the triangular achenium.: culms tufted from hard tubcrifcrous rr>ot stocks. 



15. C. Schwcinitzii, Torr. Culm rough on the angles (l-2high); 

 leaves linear; umbel simple, 4-S-rayed; spikes rroicdrd at the upper part of the 

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

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

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

 Illinois, and northwestward. Aug. Spikes .{'-$' long: the scalt-s large in 

 proportion. 



42 



