184 Cyperaceae Cyperus 



Scales straight on the back to the apex, sometimes a few near the apex of the 



spikelet with slightly curved tips in C. dentatus; stamens 2 or 3. 



Spikelets arranged in globose heads or aggregated in short clusters at the ends 



of the culms or the rays, the common rachis not more than 1 cm long. 



Inflorescence usually composed of 5 or G globose heads, usually one sessile 



or nearly so, the others on rays 2-5 (or more) cm long; culms leafy at 



the base, the leaves mostly more than 15 cm long; spikelets 4-5 mm long, 



2- or 3-flowered, usually maturing a single achene; culms with cormlike 



bases 7. C. ovularis. 



Inflorescence and plant not as above. 



Involucral bracts recurved or widely spreading at maturity, rarely one or 

 more erect; leaves narrowly linear, mostly less than 2 mm wide and 

 rarely as wide as 3 mm, the lowest leaves of the culm less than 15 cm 

 long, rarely one longer; culms below the inflorescence 0.5-1 mm in 

 diameter. 

 Spikelets in a loose or close, terminal cluster, the principal ones 8-12- 



flowered 8. C. filiculmis. 



Spikelets in compact, terminal, globose or ovoid-globose, usually solitary 

 heads, sometimes with one or two smaller heads on short rays, in 

 depauperate specimens the heads small and spikelets not compact; 

 spikelets all less than 8-flowered or only a few with 8 or more flowers. 



8a. C. filiculmis var. macilentus. 



Involucral bracts erect or ascending; culms usually more than 1 mm in 



diameter below the inflorescence; leaves linear and usually wider than 



those of the preceding group; spikelets usually in flat clusters. 



Scales scarcely or faintly nerved, their margins reddish brown, midnerve 



of scale not excurrent; culms not cormlike at the base, very leafy; 



inflorescence umbellate; spikelets very flat; style branches exserted 



more than 1 mm 9. C. dentatus. 



Scales strongly nerved, their margins hyaline; midnerve of scale excur- 

 rent; culms with cormlike bases; inflorescence racemose; style branches 

 usually not exserted, or generally not more than 1 mm. 

 Culms, leaves, and rays smooth; leaves much shorter than the culm; 

 spikelets 5-9-flowered; scales 2-2.5 mm long, the mucro less than 



0.5 mm long; achenes 1.5-2 mm long 10. C. Houghtonii. 



Culms (at least below the inflorescence), margins of leaves, and rays 

 rough; spikelets 4-16-flowered; scales mostly 3-4.5 mm long, the 



mucro usually 0.5-1 mm long; achenes 2.5-3 mm long 



11. C. Schiveinitzii. 



Spikelets arranged along an elongated rachis, the rachis usually 1-3 cm long. 

 Flowers remote, the successive scales not reaching the bases of the ones above 



on the same side of the rachilla 12. C. Engelmanni. 



Flowers approximate, the successive scales overlapping the bases of those 

 above. . 

 Scales mostly 2.75-4.5 mm long; culms with cormlike bases. 



Spikelets erect or ascending, more than 2.5 mm wide; achenes ellipsoid, 



about 2.5 mm long and half as wide 11. C. Schweinitzii. 



Spikelets widely spreading or reflexed, less than 2.5 mm wide; achenes 

 linear-oblong, mostly 1.5-2 mm long and about 0.3 mm wide except 

 in C. strigoszis var. multifiorus. 



Spikelets 4-20-flowered, stramineous, very flat 13. C. strigosus. 



Spikelets 10-35-flowered, reddish brown, terete or nearly so; achenes 

 0.75 mm wide and 2 mm long.. . .13a. C. strigosus var. multifiorus. 

 Scales less than 2.75 mm long; culms without cormlike bases. 



Scales about 1.5 mm long, reddish brown; flowers very closely imbricated, 

 the scales overlapping more than half their length; spikelets 10-40- 



