CYPERACEAE. 159 



or clustered, i-many-flowered. Scales 2-ranked or spirally imbricated, 

 persistent or deciduous. Perianth hypogynous, composed of bristles, or 

 interior scales, rarely calyx-like, or entirely wanting. Stamens 1-3, 

 rarely more. Filaments slender or filiform. Anthers 2-celled. Ovary 

 1 -celled. Ovule 1, anatropous, erect. Style 2-3-cleft or rarely simple 

 or minutely 2-toothed. Fruit a lenticular, plano-convex, or trigonous 

 achene. Endosperm mealy. Embryo minute. 



About 65 genera and 3000 species, of very wide geographic distribu- 

 tion. The dates given below indicate the time of perfecting fruit. 



Flowers of the spikelet all, or at least one of them, perfect ; spikelets all similar. 

 Scales of the spikelets 2-ranked. 



Perianth none ; spikelets in solitary or umbelled terminal heads. 



Spikelets with 2-many perfect flowers ; scales several to numerous. 



I. Cyperus. 

 Spikelets with but 1 perfect flower ; scales 2-4. 2. Kyllinga. 



Perianth of 6-9 bristles ; inflorescence axillary. 3. Dulichium. 



Scales of the spikelets spirally imbricated all around. 

 Spikelets with several to many perfect flowers. 



Base of the style swollen, persistent as a tubercle on the achene. 



Leaves reduced to basal sheaths ; bristles of the perianth usually pres- 

 ent ; spikelet solitary. 4. Eleocharis. 

 Culm leafy ; perianth-bristles none ; spikelets i-numerous. 



Spikelets capitate, involucrate. 5. Dichromena. 



Spikelets umbellate or cymose. 



Spikelets in terminal and axillary compound cymes ; most of 



the style persistent. 6. Psilocarya. 



Spikelets in a terminal umbel, base of style persistent. 



7. Stenophyllus. 

 Base of the style enlarged or narrow, deciduous. 



Flowers with no broad sepals nor interior perianth-scales. 



Style swollen at the base ; bristles none. 8. Fimbristylts. 



Style not swollen at the base ; bristles usually present. 

 Spikelets solitary to many ; bristles 1-6, rarely none. 



9. Scirpus. 

 Spikelets solitary or few ; bristles 6-many, soft, smooth, very 

 long, slender, much exserted. 10. Ertophorum. 



Flowers with a perianth of 3 stalked sepals or of 1 or 2 interior hyaline 

 scales. 

 Perianth of 3 broad stalked sepals, usually alternating with as 



many bristles. 11. Fuirena. 



Perianth of 1 or 2 hyaline scales (sepals ?) ; bristles none. 



Perianth of a single minute posterior scale. 12. Hemicarpha. 

 Perianth of 2 scales, convolute around the ovary. 



13. Lipocarpha. 

 Spikelets 1-4-flowered, some of the flowers imperfect. 



Style, or its base, persistent as a tubercle on the achene. 14. Rynchospora. 

 Style wholly deciduous. 15. Cladium. 



Flowers all monoecious or dioecious, usually borne in separate small spikelets. 

 Achene not enclosed in a utricle (perigynium). 



Spikelets clustered or solitary, not in a terminal spike ; achene bony. 



16. Scleria. 

 Spikelets forming a terminal spike; arctic genera. 



Scales 2-flowered, androgynous. 17. Elyna. 



Scales i-flowered, monoecious. 18. Kobresia. 



Achene enclosed in a utricle (perigynium). 



Axis of the pistillate flower conspicuous, subulate, often exserted beyond the 



perigynium. 19. Uncinia. 



Axis of the pistillate flower rudimentary or none, not exserted. 



20. Carex. 



1. CYPERUS L. (See Appendix.) 



Annual or perennial sedges. Culms in our species simple, triangular, leafy 

 near the base, and with I or more leaves at the summit forming an involucre to the 

 simple or compound, umbellate or capitate inflorescence. Rays of the umbel 

 sheathed at the ba=e, usually very unequal, one or more of the heads or spikes 



