2 scales in Hemicarpha\ pistillate flower surrounded by a sac in Carex); perianth 

 either of bristles or plumes or more elaborate structures or absent; fruit an achene. 

 About 4000 species in 90 genera of world-wide distribution. 



1. The unit of the infructescence (i.e., the object bearing one seed and which 

 falls from the plant at maturity) comprising not only an achene 

 and usually a portion of the style but also a thin bag surrounding 

 those structures; monoecious or dioecious 16. Carex 



1. The unit of the infructescence merely an achene with or without attached 



stylar or other floral tissue, but never surrounded by a sac (2) 



2(1). Perianth of 3 stalked scalelike or paddlelike structures, often thickened 

 at maturity, with or without 3 bristles in addition 4. Fuirena 



2. Perianth of bristles or plumose structures or absent (3) 



3(2). All or virtually all florets of each spikelet perfect (4) 



3. In each spikelet either the florets all pistillate or all staminate or merely 



some of them strictly staminate (12) 



4(3). Each achene subtended by 2 scales, the lower scale easily visible, the adaxial 

 one hyaline, very inconspicuous and often split or torn by the 

 growing achene or adhering to it 8. Hemicarpha 



4. Each achene subtended only by one abaxial scale (5) 



5(4). Culms naked, the sheath solitary on the extreme base of the culms and 

 entirely bladeless 5. Eleocharis 



5. Culms not so naked, if some of the sheaths bladeless then each culm with 



several of them (6) 



6(5). Scales of spikelets distichous and perianth bristles present; base of style 

 not much swollen but almost the entire style below the fork per- 

 sistent on the achene 1. Didichium 



6. Scales of spikelet distichous or spirally imbricate and perianth bristles present 



or absent, but if scales distichous then bristles absent; base of style 

 swollen or not, persistent or deciduous (7) 



7(6). Swollen style base persistent on the achene as a tubercle of a color and 

 texture distinct from those of the achenial body (8) 



7. Style swollen or not but not persistent on the achene (9) 



8(7). Style 3-branched; achene trigonous 6. Bulhostylis 



8. Style 2-branched; achene biconvex 14. Psilocarya 



9(7). Scales of spikelets distichous on the spikelet axis (this obscure in C. sesqui- 

 flonis, C. tenuifolius and C. brevifolius) 9. Cyperus 



9. Scales of spikelets spirally arranged (10) 



10(9). Style base swollen 7. Fimbristylis 



10. Style terete, slender, not dilated at the base (11) 



11(10). Perianth of I to 8 bristles or wanting 2. Scirpus 



11. Perianth of numerous elongate silky or woolly bristles 3. Eriophorum 



12(3). Inflorescence bracts basally white, distally green 12. Dichromena 



12. Inflorescence bracts essentially unicolored, green (13) 



13(12). Scales of spikelets visibly distichous; spikelets agglomerated into a tight 

 head 1 1. Schoeniis 



13. Scales of spikelets spirally disposed (this obscure in Scleria) or at least not 



definitely distichous (14) 



14(13). Style base enlarged and persistent as a tubercle of a color and texture 

 distinct from those of the achenial body; perianth bristles or plumes 

 usually present 13. Rhynchospora 



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