L 



CYPERACE.t. (.SKDtii: lAMII.V.) 671 



§ 3. PAPYRUS. Stifle 3-cle/l ; nchene truingular ; stamens 3 ; spikelcta mam/n 

 /lowered, flattened, the carinate scales dccurrent upon the rliachis as scarwns 

 winfjs ; spikes in simple or compound umlw/s. 



* Winr/s of the rhachis soon separatinr/ to the base as apair of free scales ; annual. 



13. C. erythrorhizos, Muhl. (PI. l, fig. 5-8.) Culm obtusely trian- 

 gular (3'-3° higli); umbel many-rayed; involucre 4-5-leave»l, very long; 

 involucels bristle-form ; spikelets very numerous, crowded in oblong «tr cylin- 

 drical nearly sessile heads or spikes, spreading horizontally, linear, Hattish (3 - 

 6" long), bright chestnut-colored ; scales lanceolate, mucronulate. — Alluvial 

 banks, L. I. to Penn., Mich., Minn., and southward ; also adventive in N. Eng. 



* * Wings of the rhachis pcrsistentlij attached ; perennial by slender running 



root stocks. 

 ■i-Achene round-obovate ; scales mucronate or acute, free or spreading. 



14. C. Haspan, L. Culms sharply angled (1 - H° high) ; leaves linear, 

 often reduced to membranous sheaths; umbel spreading , the Jii if or m raijs mostlif 

 longer than the 2-leaved involucre ; spikelets narrowly linear ; scales light reddish- 

 brown, oblong, mucronate, 3-nerv('d. — Ponds and ditches, Va. to Fla. and Tex. 



15. C. dentatus, Torr. (PI. l, fig. 9.) Culms slender (1° high) ; leaves 

 rigid and keeled; umbel erect, shorter than the 3-4-leaved involucre; scales 

 reddish-brown, icith green keel, ovate, acute, 1-nerved. — Sandy swamps, N. Eng. 

 and northern N. Y. to S. C. and W. Va. Spikes often abortive and changed 

 into leafy tufts. 



•^-■^Achene linear to oblong ; scales appressed, pointless or nearli/ so. 

 ++ Perennial by tuberiferous stolons. 



16. C. rotundus, L. (Nut-Guass.) Culm slender (|-U° high), longer 

 than the leaves; umbel simple or slightly compound, about equalling the in- 

 volucre; the few rays each bearing 4-9 dark chestnut-purple 12-40-tlowered 

 acute spikelets (4-9" long) ; scales ovate, closely appressed, nerveless except on 

 the keel. — Sandy fields, Va. to Fla. and Tex.; also adventive near Philadel- 

 phia and New York city. (Eu.) 



17. C. esculentUS, L. Culm (l -2^° high) equalling the leaves; umbel 

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

 numerous, light chestnut or straw-color, acutish, 12-30-flowered (4-7" long); 

 scales ovate or ovate-oblong narrowly scarions-margined , nerved, the acutish tips 

 rather loose ; achene oblong-obovate. (C phymatode.s, Muhl.) — Low grounds, 

 along rivers, etc., N. Brunswick to Fla., west to Minn, and Tex. ; spreading ex- 

 tensively by its small nut-like tubers and becoming a pest in cultivated grounds. 

 H- -t- Perennial, propagating by corm-like tubers from the base ; spikelets narrow, 



acuminate, often tereiish ; scales oblong-lanceolate ; achene linear-oblong. 



18. C. StrigOSUS, L. C^ilm mostly stout (I -3° high); most of the rays 

 of the umbel elongated (1 - 5'), their slieaths 2-l»ristled ; spikelets 5 - 2'^-flowered, 

 spreading; scales several-nerved, much longer than the achene. — Damp or 

 fertile soil, Canada to Fla., west to Minn., Tex., and the Pacific. Very variable 

 in the number and length of the rays of the simj)le or compound umbel, and in 

 the size of the spikelets (2-J-6 or even 12" long), more or less densely crowded 

 on the axis. 



