CYPERACEAE 



163 



ture or persistent and the spikelets falling away from the axis of the head or spike with 

 the scales attached. Scales concave, conduplicate or keeled, 2-ranked, all flower-bearing 

 or the lower ones empty. Flowers perfect. Perianth none. Stamens 1-3. Style de- 

 ciduous from the summit of the achene. Stigmas 2-3. Achene destitute of a tubercle. 

 Style-branches or stigmas 2 : achene lenticular. 

 Achene laterally compressed. 



Superficial cells of the achene oblong. 

 Superficial cells of the achene quadrate. 



Achenes oblong, linear or narrowly obovoid : plants relatively low. 

 Scales of the spikelets blunt. 



Spikelets several in each umbel. 



Scales membranous, dull : style-branches or stigmas much ex- 



serted. 

 Scales subcoriaceous, shining : style-branches or stigmas included 



or scarcely exserted. 



Spikelets 8-20 mm. long, dark green to brown. 

 . Spikelets 5-8 mm. long, yellowish green or straw-colored. 

 Spikelet solitary, appearing lateral. 

 Scales of the spikelets acute or mucronate. 

 Scales merely acute. 



Achene narrowly obovoid. 

 Achene linear to linear-oblong. 

 Scales ovate : umbel subcapitate. 



Scales oblong-lanceolate : umbel-rays usually developed. 

 Scales 2-2.5 mm. long, chestnut-brown, shining. 

 Scales 1.5 mm. long, gray-brown or straw-colored, dull. 

 Scales sharply mucronate. 



Achenes broadly obovoid to orbicular : plants relatively tall. 

 Achenes obovoid, nearly as long as the scales. 

 Achenes obovoid-orbicular, much shorter than the scales. 

 Achene dorsally compressed. 



Spikelets few, appearing lateral : one involucral bract long and erect. 

 Spikelets numerous, capitate : involucral bracts several and spreading. 

 Stvle-branches or stigmas 3 : achene trigonous. 



A. Scales falling away from the persistent rachis of the flattened spikelets. 

 a. Wings of the rachis, if any, permanently attached to it. 

 Scales tipped with recurved awns : low annuals. 



Achene 1 mm. long, narrowly obovoid : scales light brown. 

 Achene 0.5 mm. long, broadly obovoid : scales chestnut-brown. 

 Scales obtuse, acute or acuminate, not awn-tipped. 

 Wings of the rachis none, or very narrow. 



Scales of the spikelets appressed, closely contiguous. 

 Stamens 3 or 1 : scales ovate, oblong or lanceolate. 

 Stamens 3 : spikelets linear to linear-oblong. 

 Leaves not viscid. 



Scales acuminate : plants annual. 

 Scales obtuse or mucronate : plants perennial. 

 Scales obtuse : achene obovoid. 

 Scales mucronate : achene oblong. 

 Leaves viscid. 



Stamen 1 : spikelets ovate to lanceolate. 

 Scale-tips recurved. 



Annual : achene broadly oblong. 

 Perennial : achene narrowly oblong or elliptic. 

 Scale-tips straight or very nearly so : plants perennial. 

 Spikelets lanceolate to oblong-lanceolate. 

 Achene linear-oblong, stipitate. 

 Achene ovoid, not stipitate. 

 Spikelets ovate, elongating in fruit. 



Leaves, at least at the base, strongly transverse- veined 



between the nerves. 

 Leaf-blades 6-12 mm. wide: spikelets 6-14 mm. 



long. 



Leaf-blades 2-6 mm. wide : spikelets 4-6 mm. long. 

 Leaves not transversely veined between the nerves. 

 Spikelets yellow, blunt. 

 Spikelets red or reddish brown, acute. 



Stamens 2 : scales nearly orbicular or obovate, mucronulate. 

 Scales of the spikelets not appressed, distant. 

 Spikelets linear-filiform, spicate. 



Spikelets merely linear or oblong-linear, densely capitate. 

 Wings of the rachis distinct. 



Scapes not transversely septate, 3-angled. 

 Leaves reduced to pointed sheaths. 

 Leaves with elongated linear blades. 

 Scales mucronate. 

 Scales not mucronate. 

 Spikelets 3-4 mm. wide. 

 Spikelets 1.5-2 mm. wide. 



Scales wholly or partially purple-brown : achene linear 



oblong. 



Scales tightly appressed throughout. 

 Scales with free tips. 

 Scales straw-colored : achene obovoid. 

 Scapes transversely septate, terete. 



1. C. flavescens. 



2. C. diandrus. 



3. C. rivularis. 



4. C. helvus. 



5. C. bipartitus. 



6. C. Nuttallii. 



7. C. microdontus. 



8. C. Gatesii. 



!9. C. polystachyus. 



10. C. pumttus. 



11. C. flavicomus. 



12. C. Hochstetteri. 



13. C. laevigatus. 



14. C. Careyi. 



15. C. inflexus. 



16. C . squarrosus. 



17. C. compressu8. 



18. C. Buckleyi. 



19. C. Biishii. 



20. C. elegans. 



21. C. acuminatus. 



22. C. cyrtolepis. 



23. C. Drummondii. 



24. C. ochraceus. 



25. C. virens. 



26. C. pseudovegetus. 



27. C. Surinamensis. 



28. C. reflexus. 



29. C. Iria. 



30. C. distans. 



31. C. cephalanthus. 



32. C. Haspan. 



33. C. dentatus. 



34. C. multiradiatus. 



35. C. rotundus. 



36. C. Hallii. 



37. C. esculentus. 



38. C. articulatus. 



