CYPEKACE^E. (SEDGE FAMILY.) 571 



3. PAPYRUS. Style 3-cleft ; achene triangular ; stamens 3 ; spikelets many- 

 flowered , flattened , the carinate scales decurrent upon the rhachis as scarious 

 wings ; spikes in simple or compound umbels. 



# Wings of the rhachis soon separating to the base as a pair of free scales ; annual. 



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

 gular (3'-3 high); umbel many-rayed; involucre 4-5-leaved, very long; 

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

 drical nearly sessile heads or spikes, spreading horizontally, linear, flattish (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 persistently attached ; perennial by slender running 



rootstocks. 

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



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

 often reduced to membranous sheaths ; umbel spreading, the filiform rays mostly 

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

 brown, oblong, mucronate, 3-nerved. Ponds and ditches, Va. to Fla. and Tex. 



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

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

 reddish-brown, with green keel, ovate, acute, 7-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 nearly so. 

 M- Perennial by tuberiferous stolons. 



16. C. rottindus, L. (NUT-GRASS.) Culm slender (i-lj 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 } 2 - 40-flowered 

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

 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 scarious-margined , nerved, the acutish tips 

 rather loose ; achene oblong-obovate. (C. phyinatodes, 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. 

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



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



18. C. strigOSUS, L. Culm mostly stout (1-3 high); most of the rays 

 of the umbel elongated (1 - 5'), their sheaths 2-bristled ; spikelets 5 - 25 -flowered t 

 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 simple or compound umbel, and in 

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



on the axis. ne , 

 25 



