CYPERACEAE 



181 



angles and appearing turgid. Base of the style presistent 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. 1. E. interstincta. 



Achenes copiously pitted : scapes continuous. 2. E. cellulosa. 



Scapes sharply 4-angled : achenes cancellate. 3. E. mutata. 



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



Spikelet 6-8-flowered : achenes about 2 mm. long, deeply pitted : scapes 3- 



angled. 4. E. RobUnsii. 



Spikelet 12-20-flowered : achenes about 1 mm. long, faintly pitted : scapes 



terete. 5. E. elongata. 



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. 6. E. ochreata. 



Scales brown : perianth-bristles shorter than the achene. 7. E. praticola. 



Achenes about 1 mm. long. 



Scapes 2-10 cm. long: perianth-bristles longer than the achene. 8. E. olivacea. 



Scapes 10-35 cm. long : perianth-bristles as long as the achene. 9. E. maculosa. 



Upper sheath truncate, oblique or toothed, not scarious. 

 Annuals with fibrous roots. 



Scapes capillary : spikelets with 1-4 achenes. 10. E. capiUacea. 



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. 11. 



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



cm. tall. 12. 



Achenes pale brown to white. 



E. atropurpurea. 

 E. capitata. 

 E. bicolor. 



Scapes filiform : achene white. 13. 



Scapes slender : achenes pale brown. 

 Scales of the spikelets obtuse. 



Perianth-bristles longer than the achene : spikelets ovoid. 14. E. obtusa. 

 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. 

 i 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. 34. E. arenicola. 



Scapes flattened : scales acute. 35. E. acuminata. 



Spikelets linear-cylindric : achene constricted at the neck. 36. E. cylindrica. 



Tubercle long-conic, scarcely distinguishable from the achene. 37. E. rostellata. 



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

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



23. 



E. Engelmannii, 

 E. lanceolata. 



E. nodulosa. 

 E. macrostachya. 



E. glaucescens. 

 E. Ravenelii. 



E. acicularis. 

 E. Chaetaria. 

 E. vivipara. 



E. tortilis. 



E. tuber culosa. 



E. Torreyana, 

 E. microcarpa. 



E. melanocarpa. 

 E. albida. 



32. E. tricostata. 



33. E. tennis. 



