CYPERACEAE 



181 



angles and appearing turgid. Base of the style presisteiit on the summit of the achene, 



forming a tubercle. 



Spike Rush. 



Spikelet scarcely or not at all thicker than the scape : scales mostly leathery. 

 Bristles 6, as long as the achene or shorter : scapes relatively stout. 

 Scapes terete, at least above : achenes not cancellate. 

 Achenes transversely ridged : scapes nodose-septate. 

 Achenes copiously pitted : scapes continuous. 

 Scapes sharply 4-angled : achenes cancellate. 

 Bristles 7, longer than the achene : scapes relatively slender. 



Spikelet 6-S-flo\vered : achenes about 2 mm. loiig, deeply pitted : scapes 3- 



angled. 

 Spikelet r2-20-flowered : achenes about 1 mm. long, faintly pitted : scapes 

 terete. 

 Spikelet manifestly thicker than the scape : scales mostly membranous. 

 Style-branches or stigmas 2 : achene lenticular or biconvex. 



Upper sheath scarious, hyaline : plants perennial by slender rootstocks. 

 Achenes about 0.5 mm. long. 



Scales pale green or rarely white: perianth-bristles longer than the 



achene. 

 Scales brown : perianth-bristles shorter than the achene. 

 Achenes about 1 mm. long. 



Scapes 2-10 cm. long : perianth-bristles longer than the achene. 

 Scapes 10-35 cm. long : perianth-bristles as long as the achene. 

 Upper sheath truncate, oblique or toothed, not scarious. 

 Annuals with fibrous roots. 



Scapes capillary : spikelets with 1-4 achenes. 

 Scapes slender : spikelets with several to many achenes. 

 Achenes black. 



Perianth-bristles 2-4, pale : achenes 0.5 mm. long : scapes 2-9 cm. 



tall. 

 Perianth-bristles 5-8, brown : achenes 1 mm. long : scapes 5-25 

 cm. tall. 

 Achenes pale brown to white. 

 Scapes filiform : achene white. 

 Scapes slender: achenes pale brown. 

 Scales of the spikelets obtuse. 



Perianth-bristles longer than the achene 

 Perianth-bristles not longer than the achene, often short or 

 wanting : spikelets cylindric. 

 Scales of the spikelets acute. 

 Perennials with horizontal rootstocks. 

 Scapes nodose-septate. 

 Scapes continuous. 



Scales pale green or straw-colored : scape relatively stout. 

 Scales brown or dark green: scapes slender or filiform. 

 Achenes 1.5 mm. long : tubercle conic. 

 Achenes 1 mm. long or less : tubercle depressed. 

 Style-branches or stigmas 3 : achene 3-angled;or turgid. 

 Achene cancellate. 



Achene longitudinally ribbed. 

 Achene not longitudinally ribbed. 



Scapes filiform : spikelets with 1-4 achenes. 

 Scapes slender : spikelets with many achenes. 

 Spikelets linear-oblong, often proliferous. 

 Spikelets ovoid to conic-ovoid, not proliferous. 

 Tubercle conic, smaller than the achene. 

 Tubercle cap-like, as large as the achene or larger. 

 Achene smooth, papillose, or irregularly ridged-reticulated. 

 Scapes capillary or filiform. 



Spikelets terete or nearly so, 6-2- flowered. 

 Spikelets oblong, 3-6 mm. long. 

 Spikelets ovoid, 2-3 mm. long. 

 Spikelets flattened. 2-6-flowered, often proliferous. 

 Achene obovoid : tubercle deltoid or depressed. 

 Achene oblong : tubercle abruptly subulate-tipped. 

 Scapes slender or stout. 



Tubercle plainly distinguishable from the achene. 



Spikelets ovoid to oblong : achene not.constricted at the neck. 

 Achenes smooth. 



Tubercle flat, covering the top of the black achene. 

 Tubercle ovoid-conic, acute, contracted at the base. 

 Achenes papillose or irregularly ridged-reticulated. 

 Achenes with the 3 angles ribbed. 

 Achenes obtusely 3-angled. 



Scapes slender to nearly filiform : scales obtuse. 



Bristles 2-4, shorter "than the achene : achene strongly 



papillose to reticulated. 

 Bristles 6, the longer as long as the achene : achene 

 faintly reticulated. 

 Scapes flattened : scales acute. 

 Spikelets linear-cylindric : achene constricted at the neck. 

 Tubercle long-conic, scarcely distinguishable from the achene. 



1. E. interstincta. 



2. E. cellulosa. 



3. E. mutata. 



4. E. Robbinsii. 



5. E. elongata. 



6. E. ochreata. 



7. E. praticola. 



8. E. oUvacea. 



9. E. maculosa. 



10. E. capillacea. 



11. E. atropurpurea. 



12. E. capitata. 



13. E. bicolor. 



spikelets ovoid. 14. E. obtusa. 



15. E. Engelmannii. 



16. E. lanceolata. 



17. E. nodulosa. 



18. E. macrostachya. 



19. E. glaueescem. 



20. E. Savenelii. 



21. E. acicularis. 



22. E. Chaetaria. 



23. E. vivipara. 



24. E. tortilis. 



25. E. tuberculosa. 



26. E. Torreyana. 



27. E. microcarpa. 



28. E. prolifera. 



29. E. Baldwinii. 



30. E. melanocarpa. 



31. E. albida. 



32. E. tricostata. 



33. E. tenuis. 



34. E. arenicola. 



35. E. acuminata. 



36. E. cylindrica. 



37. E. rostellata. 



1. Eleocharis interstincta (Vahl) R. & S. Perennial by stout rootstocks. Scapes 

 terete, hollow, nodose-septate, 4-9 dm. tall, the sterile ones sharp-pointed : sheaths mem- 



