46 CYPERACEAE 



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". Aniericanus. 

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

 Involucral bract erect. 7. S. Torreyi. 



Involucral bract abruptly bent. 8. 5". mucronatus. 



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



9. 5'. lacuslris. 

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



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



10. S. fluviaiilis. 

 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. atrovireyis. 



Stigmas 2: achene lenticular : perianth-bristles 4. 13. 6". rubrotinctus. 

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



14. S. polyphyllus. 

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



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



15. S. litiealtts. 

 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 di.stinctlypeduncled. 17. S. Eriophoriim. 



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



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



1. Scirpus pauciflorus Ligbtf . Few-flowered Club-rush. (Man. 

 p. 176; I. F.y^ 610.) 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 Club-rush. (Man. p, 176; I. F. 

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

 Northampton ; Chester ; Monroe ; Lancaster ; Huntingdon ; 

 Allegheny ; Lvcoming ; Berks ; Somerset. 



3. Scirpus subterminalis Torr. Water Club-rush. (Man. p. 176; 

 I. F. y. 614.) In ponds or streams or sometimes on their borders, N. B. 

 to the N. W. Terr., Wash., N. J., Pa. and Mich. — Pentisylvatiia : Mon- 

 roe; Carbon; Erie, Presque Isle; Lackawanna. 



