110 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



14. CYPEKACEAE. Sedge Family. 



Grasslike or rushlike herbs; stems usually solid; roots fibrous; leaves narrow, with 

 closed sheaths, the whole leaf sometimes reduced to a sheath; flowers perfect or 

 unisexual, arranged in spikelets, one in the axil of each scale, the spikelets solitary or 

 clustered, 1 to many-flowered; perianth of bristles or wanting; stamens 1 to 3; styles 

 2 or 3; fruit a lenticular or trigonous achene. 



KEY TO THE GENERA. 



Flowers all unisexual, usually in separate spikes. 



Achenes inclosed in a perigynium; glumes 1-flowered . 8. Carex (p. 116). 

 Achenes not inclosed in a perigynium; glumes 



2-flowered 9. Kobresia (p. 124). 



Flowers all, or at least part of them, perfect; spikelets 

 similar. 

 Scales of the spikelets 2-ranked; spikelets more or less 



flattened 1. Cyperus (p. 110). 



Scales of the spikelets imbricated spirally in several 

 ranks; spikelets not flattened. 



Perianth bristles much elongated, woolly 7. Eriophorum (p. 116). 



Perianth bristles short or wanting. 



Spikelets 1 to 4-flowered; plants large, about 



1 meter high, leafy 2. Clabium (p. 112). 



Spikelets several to many-flowered; plants 

 mostly low. 

 Base of the style persistent, enlarged. 

 Leaves reduced to sheaths; spikelets 



solitary 3. Eleocharis (p. 112). 



Leaves not reduced ; spikelets several, 



mostly paniculate 4. Stenophyllus (p. 114). 



Base of the style deciduous, enlarged or 

 narrow. 



Perianth consisting of bristles 5. Scirpus (p. 114). 



Perianth of a single hyaline scale 6. Hemicarpha (p. 116). 



1. CYPERUS L. 



Tufted or simple-stemmed annuals or perennials, 50 cm. high or less, with basal 

 leaves and triangular stems, the flowers in headlike clusters or unequally branched 

 Umbels subtended by leaflike bracts; spikelets flattened or cylindric; glumes decid- 

 uous, or if persistent the spikelets falling entire, 2-ranked; flowers perfect; perianth 

 none; stamens 1 to 3; achene without a tubercle. 



key to the species. 



Annual; plants small, 5 to 15 cm. high ; tips of the bracts subulate, 



conspicuously reflexed; inflorescence capitate 1. C. inflexus. 



Perennials (rarely annual); plants taller, more than 15 cm. high; 

 tips of the bracts mostly erect, rarely spreading; inflores- 

 cence various. 

 Spikelets ovate to ovate-oblong (4 to 5 mm. long, crowded at 



the ends of the rather long, subequal rays of the umbel) . 2. C cyrtolepis. 

 Spikelets linear to narrowly oblong. 



Spikelets narrowly oblong; scales of the flowers not over- 

 lapping, especially in fruit (very strongly nerved). 

 Inflorescence crowded, subcapitate 3. C.fendlerianus. 



