CYPERACEAE (SEDGE FAMILY) 



181 



6. Achenes triangular or turgid ; style 3-cleft g. 

 g. Acheues regularly reticulate or cross-lined.' 



Spikelets flattened, 3-9-tIowered ; the thin scales 2-3-ranked . 13. E. acicularis. 

 Spikelets terete ; the scales many-ranked. 



Upper sheaths loose, with white scarious tips ; achenes 



finely cross-lined between the strong ribs . . . .14. E. Wolfii. 

 Upper sheaths close and firm, not scarious ; achenes distinctly 



reticulate. 



Tubercle conic-subulate, much smaller than the achene . 15. E. tortilis. 

 Tubercle cap-shaped, as large as the achene . . .16. E. tuberculosa. 

 g. Achenes smooth or papillose, not regularly reticulate h. 

 h. Tubercle depressed, as broad as high or broader. 



*. Achenes white 17. E. Torreyana. 



i. Achenes yellow, brown, or black j. 

 j. Achenes smooth. 



Tubercle flattened and closely covering the top of the 



black achene 18. E. mefanocarpa. 



Tubercle short-conic, constricted below, narrower than 



the olive-brown achene 19. E. albida. 



j. Achenes papillose-roughened. 



Achene with prominent keel-like angles . . . . 20. E. tricostata. 

 Achene with the angles not keeled. 

 Tips of the upper sheaths dark -girdled ; achenes 

 golden-yellow or orange-brown (in age drab), 

 conspicuously papillose-roughened, plump, with 

 rounded angles. 



Culms filiform, 4-angled 21. E. tennis. 



Culms flattened 22. E. acuminata. 



Tips of the upper sheaths whitish ; achenes whitish- 

 yellow, minutely roughened, with distinct angles 23. E. nitida. 

 h. Tubercle long-conic, higher than broad. 



Tubercle clearly distinct from the achene. 

 Tubercle conic-subulate, much narrower than the plump 

 achene. 



Bristles exceeding the achene 24. E. intermedia. 



Bristles wanting (24) E. intermedia, v. Ilabereri. 



Tubercle conic-deltoid, nearly as broad as the compressed 



achene 25. E. Macounii. 



Tubercle seemingly confluent with the achene . . .26. E. rostellata. 



238. E. interstincta. 



1. E. interstincta (Vahl.) R. & S. Culms large and stout 

 (0.5-1 m. high), knotted as if jointed by many cross-partitions; 

 basal sheaths often leaf-bearing ; spikelets 2-4 cm. long ; scales 

 in several ranks, pale, with scarious mar- 

 gins ; achene with transversely linear-rec- 

 tangular reticulation and a conical-beaked 

 tubercle ; bristles 6, rigid, or wanting. (E. 

 equisetoides Torr.) Shallow water, Mass. 

 to Fla., w. to Mich, and Tex. (W. I., 

 S. A.) FIG. 238. 



2. E. quadrangulata (Michx.) R. & S. 

 Similar ; culm continuous and sharply 



^-angled; spikelet 2-0 cm. long ; achene finely reticulated, 

 with a conical flattened distinct tubercle. (E. mutata 

 Britton, not R. & S.) Shallow water, Ct. to Mich., and 

 southw., rare. FIG. 239. 



3. E. Robbinsh Oakes. Flower-bearing 

 culms exactly triangular, rather slender, 



erect (2-7 dm. high), also producing tufts of capillary abortive 

 steins or fine leaves, which float in the water ; sheath obliquely 

 truncate ; spikelet l-2.. r > mm. long ; scales only 

 3-9, few-ranked, convolute-clasping the long 

 flattened joints of the axis, lanceolate, with thin 

 scarious margins; achene oblong-obovate, tri- 

 angular, minutely reticulated, about half the 

 length of the bristles, tipped with a flattened awl-shaped tubercle. 

 241. E. ochreata. Shallow water, N. B. to Fla., w. to Mich, and Ind. FIG. 240. 

 4. E. ochreata (Nees) Steud. Similar in habit to the next; 

 the capillary culms 3-30 cm. high ; spikelets 2-6 mm. long ; scales 



239. E. quadrangulata. 



240. E. Eobbinsii. 





Spikelet x 2%. 

 chene x 10. 



