14. Style base not persistent; perianth absent (15) 



15(14). Achene often bony, pearly or crustaceous, supported on a disk or 

 appearing sculptured basally; pistillate flowers solitary and borne 

 in separate spikelets 15. Scleria 



15. Achene otherwise; spikelets all alike and borne in very large inflorescences 



10. Cladium 



1. Dulichium Pers. 



The genus comprises only one species; confined to North America. 

 1. Dulichium arundinaceum (L.) Britt. Three-way sedge. Fig. 174. 



Perennial with creeping rhizomes 2-3 mm. thick and with internodes 2-5 cm. 

 long; culms simple, solitary from the nodes of the rhizomes, 2-10 dm. long, 2-5 

 mm. thick, erect, with short internodes; lowest leaves with nearly bladeless sheaths, 

 the upper with short stiff pointed ascending blades 2-10 cm. long, the upper 5 to 

 20 leaves functioning as bracts, each subtending a peduncled spike; peduncle of 

 spike only slightly longer than the bract sheath; spike 2-6 cm. long, 15-50 mm. 

 thick, of 6 to 15 ascending to eventually spreading spikelets; spikelets of 5 to 10 

 distichous scales, the axis with each internode thickened and concave (niched) on 

 the fertile side and with 2 narrow vertical wings at the edges of the niche; perianth 

 bristles 6 to 9, coarse, longer than the achene, retrorsely serrate; style branches 2; 

 achene flattened, beaked with the long persistent style. 



Infrequent or rare in boggy places, edge of streams and swamps, e. Tex. 

 (Leon, Robertson, Cass, Madison, Henderson and Wood cos.), fall; wet places 

 and in shallow water over much of the lowlands of U.S., n. to Nfld., Que., Ont. 

 and B.C., s. to the Gulf States and Calif. 



2. Scirpus L. Bulrush 



Annual or perennial herbs, usually aquatic; leaves either well-developed or 

 the blades much-reduced in some species; inflorescences very variable; scales of 

 spikelets spirally imbricate; each flower with only a single subtending scale; 

 bristles present or rarely absent; styles 2- or 3-branched; achenes plano-convex, 

 biconvex or trigonous, usually apiculate but the apex of the same texture and 

 color as the rest of the achene (not differentiated as a "tubercle"); style completely 

 deciduous. 



About 300 species, cosmopolitan. 



1. Bracts leaflike, none appearing as a continuation of the culm (2) 



1. Primary bract appearing as a continuation of the culm and similar to it in 



texture, color and usually in transectional outline (10) 



2(1). Spikelets in dense spherical or prolate heads 1-2 cm. thick 



1.5. cuhensis. 



2. Spikelets either solitary on their peduncles or in small fascicles or glomerules, 



never in dense heads (3) 



3(2). Achene 3-5 mm. long (4) 



3. Achene about 1 mm. long (5) 



4(3). Achene dull gray-brown, 4-5 mm. long; bristles 6, stiff, retrorsely barbed 

 2. S. ftuviatilis. 



4. Achene dark-brown to black, 3>-^ mm. long; bristles 2 to 6, fragile or 



deciduous 3. S. maritiinus. 



5(3). Bristles very long and far-surpassing the scales, conspicuous in fruit 



4. S. cyperinus. 



5. Bristles mostly shorter than the scales or if longer then never exserted from 



the spikelet (6) 



344 



