46 CYPBRACEAE 



Spikelets few, 1-12, appearing lateral. • 

 Annual plants, with bluntly 3-angled scapes : achenes plano-convex. 

 Perianth-bristles about as long as the achene, downwardly barbed. 



4. 5. debilis. 

 Perianth-bristles minute or obsolete. 5. 5. Smithii. 



Perennial plants, with sharply 3-angled scapes. 

 Perianth-bristles mostly shorter than the achene : achene plano-convex. 



6. 5. Americanus. 

 Perianth-bristles mostly longer than the achene : achene 3-angled. 

 Involucral bract erect. 7. S. Torreyi. 



Involucral bract abruptly bent. 8. S. mucronatus. 



Spikelets several or numerous, in umbels or umbel-like clusters. 



9. 5. lacustris. 

 B. Involucre of 2 or more bracts with flat blades. 

 Spikelets few to several, capitate to umbellate, relatively large. 



10. S. fluviatilis. 

 Spikelets very numerous, in compound umbels or umbelled heads, relatively 

 small. 

 Perianth-bristles downwardly barbed or wanting : spikelets in umbelled 

 heads. 

 Perianth-bristles equalling or slightly exceeding the achenes : leaf -blades 

 6-16 mm. wide. 

 Stigmas 3 : achene 3-angled : perianth-bristles 6. 

 Spikelets 3-8 in each head : scales obtuse : perianth-bristles barbed 



throughout. 11. S. sylvaticus. 



Spikelets 8-20 in each head : scales acute : perianth-bristles not 

 barbed below. 12. S. atrovirens. 



Stigmas 2J: achene lenticular : perianth-bristles 4. 13. 5. rubrotinctus. 

 Perianth-bristles twice as long as the achene : leaf-blades 4-6 mm. wide. 



14. 5. polyphyllus. 

 Perianth-bristles smooth or slightly pubescent : umbel mostly decompound. 



Perianth-bristles shorter than the scales or scarcely exceeding them. 



15. S. Uneatus. 

 Perianth-bristles much exserted beyond the scales at maturity. 



Bracts of the involucre reddish at the base : scales and bristles reddish. 



Spikelets sessile, in small heads. 16. 5. cyperinus. 



Spikelets or some of them distinctly peduncled. 17. 5. Eriophorum. 



Bracts of the involucre blackish at the base : scales greenish black r 



bristles brown or olive-brown. 18. 5. atrocinctus. 



1. Scirpus paucifloruB Ligbtf. Few-flowerEd Ci,ub-rush. " (Man. 

 p. 176 ; I. F./. 6io.) In wet soil, Anticosti and Ont. to B. C, Pa. and in 

 the Rocky Mountains to Col., and in the Sierra Nevada. Also in Eu. 

 — Pennsylvania : Erie, Presque Isle. 



2. Scirpus planifolius Muhl. Wood Ci<ub-rush. (Man. p. 176 ; I. F. 

 /. 6/j. ) In woods and thickets, R. I. to Mo. and Del. — Pennsylvania : 

 Northampton ; Chester ; Monroe ; Lancaster ; Huntingdon ; 

 Ai,i,EGHENY ; Lycoming ; Berks ; Somerset. 



3. Scirpus subteiminalis Torn Water Ci<ub-rush. (Man. p. 176; 

 I. P./. 614.) In ponds or streams or sometimes on their borders, N. B. 

 to the N. W. Terr., Wash., N. J., Pa. and ^ich.— Pennsylvania : Mon- 

 roe ; Carbon ; Erie, Presque Isle ; Lackawanna. 



