256 



CYPERACEAE 



cate or keeled, 2-ranked, all flower-bearing or the lower ones empty. Flowers perfect. 

 Perianth none. Stamens 1-3. Style 2-3-cleft, deciduous from the summit of the achene. 

 [Ancient Greek name for these sedges.] 



About 600 species, of wide distribution in tropical and temperate regions. Type species, Cypcrus 

 esculentus L. 



Style-branches 2; achene lenticular. 

 Achene laterally flattened. 

 Spikelets 2-2.5 mm. wide. 



Spikelets in a single capitate cluster. 

 Spikelets in umbeled clusters. 

 Spikelets about 5 mm. wide. 

 Achene dorsally flattened. 

 Style-branches 3; achene trigonous. 



Spikelets flattened, not breaking up at the nodes. 



Rachis of the spikelet persistent, the scales falling away from it. 

 Rachis-wings very narrow, or none. 

 Annuals with fibrous roots. 

 Spikelets capitate. 

 Scales awned. 

 Scales acute. 

 Spikelets spicate. 

 Perennials, with rootstocks. 



Spikelets subcapitate; base of the culm tulicr-like; stamens 3. 

 Spikelets digitate; base of the culm not tuber-like; stamen 1. 

 Rachis distinctly winged. 



Perennial by tuberiferous rootstocks; rachis-wings persistent. 

 Scales straw-color; achene obovoid. 

 Scales purjjle-brown; achene linear-oblong. 

 Annual; rachis-wings separating. 

 Spikelets falling away from the 2 lower empty scales. 



Spikes loose, not densely cylindric, with two to several achenes. 

 Spikelets distinctly flattened. 

 Spikelets little flattened. 

 Spikes densely cylindric; spikelets about 3 mm. long, with only 1 achene. 15. 

 Spikelets subterete, breaking up at the nodes into 1-fruited joints. 16. 



1. Cyperus melanostachys H. B. K. 

 Brown Cyperus. Fig. 608. 



Cypcrus melanostachys H. B. K. Nov. Gen. 1: 207. 1815. 

 Cyperus diaiidrus capitatns Britton, Bull. Torrey Club 13: 205. 



10. 

 11. 

 12. 



13. 



14. 



C. inflcxus. 



C. actiminatus. 



C. parishii. 



C. bushii. 



C. vegetus. 



C. esculentus. 



C. rotundus. 



C. crvthrorrhisos. 



C. strigosus. 



C. hanseui. 



C. regiomontanus. 



C. fera.v. 



1886. 



Rootstocks short ; roots fibrous. Culms glabrous, slen- 

 der, trigonous, tufted, 1-6 dm. high. Leaves glabrous, 

 shorter than the culm or equaling it, 1-3 mm. wide, those 

 of the involucre about 3, sometimes much elongated ; 

 inflorescence a capitate cluster of spikelets, rarely with one 

 umbel-ray bearing a sinaller cluster; spikelets lanceolate, 

 acute or acutish, 5-12 mm. long, about 2.5 mm. wide ; scales 

 ovate, acutish or obtuse, brown or green-brown ; achene 

 oblong, pointed, its superficial cells quadrate. 



Wet grounds of the Sonoran Zones; California northward to Butte 

 County; Arizona to Texas and Mexico; Colombia. Referred by 

 Watson to C. diaiidr}ts castaneus Torr. Type locality: Colombia. 



2. Cyperus rivularis Ktinth. 

 Shining Cyperus. Fig. 609. 



Cypcrus ri'iUlaris Kunth, Enum. 2: 6. 1837. 



Culms slender, tufted, 1-4 dm. high. Umbel 

 usually simple; spikelets linear or linear-oblong, 

 acutish, 8-20 mm. long ; scales green or dark brown, 

 or with brown margins, appressed, firm, subcoriace- 

 ous, shining, obtuse ; stamens mostly 3 ; style 2-cleft, 

 scarcely exserted ; achene oblong or oblong-obvate, 

 lenticular, somewhat pointed, dull, its superficial cells 

 quadrate. 



Wet soil. Transition or Canadian Zone; Sisson, California; 

 Michigan to Kansas, Ontario, Maine, and North Carolina. 

 Type locality: Georgia. 



