CTPEKACEAE. 39 



Perianth wanting. 



Achenes tuberculate at the apex. 6. Pimbristylis. 



Achenes not tubercuhite. 7. Stenophxllus. 

 Spikelets polygamous. 



Stigmas 3 : style deciduous. 8. Mariscus. 



Stigmas 2: style persistent. 9. Rxnchospoba. 

 Spikelets with monoecious or dioecious flowers. 



Achene not enclosed In a utricle (perigynium). 10. Scleria. 



Achene enclosed in a utricle (perigynium). 11. Carex. 



1. DUIjICHIUM L. C. Kich. Perennial caulescent herbs, with terete, 

 hollow, conspicuously jointed stems. Lower leaves mere sheaths. Spikes axil- 

 lary, pedunclecl. Spikelets 2-ranked, flat, very narrow, 6-10-flowered. Scales 

 2-ranked, carinate, decurrent. Perianth of 6-9 retrorsely barbed bristles. Sta- 

 mens 3. Style persistent. Stigmas 2. Achenes narrow, beaked. 



1. D. anindinaceum (L.) Britton. Stems 3-10 dm. tall: leaves numerous; 

 blades flat, 2-8 cm. long, spreading or ascending: spikelets narrowly linear, 

 spreading, 1-2.5 cm. long; scales lanceolate, acuminate, strongly several-nerved, 

 appressed, brownish: bristles rigid, longer than the achene: achenes linear- 

 oblong. [D. spathaceum (L.) Pers.] — Occasional in swamps. — Sum. 



2. CYPERUS [Tourn.] L. Annual or perennial scapose herbs. Leaves 

 basal: blades narrow. Scapes simple, triangular, with one or more bracts at 

 the summit forming an involucre to the simple .or compound, umbellate or capi- 

 tate inflorescence. Eays of the umbel sheathed at the base, usually very unequal. 

 Spikelets flat or nearly terete, the scales falling away from the rachis as they 

 mature or persistent and the spikelets falling away from the axis of the head 

 or spike with the scales attached. Scales 2-ranked, all flower-bearing, or the 

 lower ones empty. Perianth none. Stamens 1-3. Style deciduous. Stigmas 

 2 or 3. Achene beakless. — Galingale. 



Style-branches or stigmas 2 : achene lenticular. 



Achenes suborblcular, the superficial cells oblong. 1. C. flavescens. 



Achenes oblong to obovoid, the superficial cells quadrate. 

 Splkelet-scales dull : style-branches or stigmas con- 

 spicuously exserted : stamens 2. 2. C. diandrus. 

 Splkelet-scales shining : style-branches or stigmas 



scarcely exserted : stamens 3. 3. C. rivularis. 



Style-branches or stigmas 3 : achenes three-angled. 



Scales falling away from the persistent rachis of the 

 flattened spikelets. 

 Splkelet-scales with recurved awn-tips : plants an- 

 nual. 4. C. inflexus. 

 Splkelet-scales acute or mucronate : plants perennial. 

 Spikelets mainly reddish-brown ; scales with las 



mucronate tips. 5. C. dentatua. 



Spikelets mainly straw-colored or pale-brown ; 



scales with acute tips. 6. C. esculentus. 



Scales and rachis of the spikelets falling away. 



Achenes narrowly linear-oblong, 2%-4 times as long 

 as thick. 

 Spikelets decidedly flattened, several-many-flow- 

 ered. 7. C. strigostis. 

 Spikelets nearly terete, 1-few-flowered. 



Spikelets borne in a loose spike. 8. C. refractus. 



Spikelets borne in a dense or head-like spike. 



Spikes globular : spikelets spreading. 9. C. ovtilaris. 



Spikes cyllndrlc to oval or obovoid : 



spikelets becoming refracted. 10. C. lancastriensis. 



Achenes oblong or obovoid, less than twice as long 



as thick. 11. C. filiculmis. 



1. C. flavescens L. Annual. Leaves yellowish-green: scapes very slender, 

 tufted, 7-30 cm. tall: spikelets linear, yellow, many-flowered, flat, 8^18- mm. 

 long, the clusters terminal and sessile, or on 1-4 short rays: scales short. 



