164 



CYPEEACEAE 



b. Wings of the rachis separating from it as interior scales : annuals. 

 Spikes loose, or if dense not narrowly cylindric : spikelets 6-25 mm. long. 



Spikelets crowded : scales loose. 39. C. erythrorhizos. 



Spikelets not crowded : scales closely appressed. 40. C. digitalus. 



Spikes very dense, cylindric : spikelets 3-5 mm. long. 41. C. Halei. 



B. Rachis of the spikelets deciduous. 



Rachis breaking up into 1-fruited joints : spikelets nearly terete. 



Spikes solitary : scapes filiform : plants perennial. 42. C. Floridanus. 



Spikes umbellate or capitate-congested : scapes stout to slender : 



plants annual. 



Scales of the spikelets distant : achene linear-oblong. 43. C. EngelmanniL 



Scales of the spikelets manifestly imbricated : achene obovoid. 

 Spikelets relatively loosely spicate. 



Spikes dull brown : scales thin, not tightly appressed. 44. C. speciosus. 



Spikes yellowish or grayish brown : scales firm, appressed. 45. C. ferax. 



Spikelets densely congested into 1-4 heads. 



Inflorescence umbellate : spikes disposed at the ends of the 2-4 



rays of the umbel. 46. C. Eggersii. 



Inflorescence capitate: spikes collected into a terminal con- 

 gested cluster. 47. C. oxycarioidcs. 

 Rachis deciduous above the lower pair of scales : plants perennial by hard 



corm-like tubers. 



Achene narrowly linear-oblong, 2%-4 times as long as thick. 

 Spikelets distinctly flattened, several-many-flowered. 



Spikelets in dense globular heads. 48. C. Martindalei. 



Spikelets loosely spicate or relatively so. 



Spikelets chestnut^brown. 49. C. setigerus. 



Spikelets yellow to yellow-brown. 



Scales appressed. 50. C. strigosus. 



Scales loose, somewhat spreading. 51. C. stenolepis. 



Spikelets nearly terete to a little flattened, 1-few-flowered. 

 Spikelets loosely spicate. 



Spikelets 1-2 cm. long : achene about 3 mm. long. 52. C. refractus. 



Spikelets less than 1 cm. long : achene 1.5 mm. long. 53. C. dissitiflorus* 



Spikelets capitate or capitate-spicate. 



Spikelets all reflexed : scapes almost always rough. 54. C. retrofradus. 



Spikelets spreading or only the lower ones reflexed : scapes 



smooth. 

 Spikes or heads dense, cylindric to globose. 



Spikes globose. 55. C. ovularis. 



Spikes cylindric to oval or obovoid. 



Spikelets 3-7 mm. long : spikes obovoid or cylindric. 



Spikes obovoid : lower spikelets reflexed. 56. C. retrorsus. 



Spikes cylindric. 



Spikes 0.5-2 cm. long, simple. 



Spikelets 3-4 mm. long, 1-2-flowered. 57. C. cylindricuK. 



Spikelets 5-7 mm. long, 3-4-flowered. 58. C. Plankii. 



Spikes 1.5-3.5 cm. long, usually compound. 59. C. cylindrostachys. 



Spikelets 8-10 mm. long: spikes oval. 60. C. Lancastrientis. 



Spikelets loosely spicate or capitate. 



Spikelets 8-12 mm. long, subulate. 61. C. uniflorus. 



Spikelets 3-5 mm. long, not subulate. 62. C. mbuniflorus. 



Achene oblong to obovoid, not more than twice as long as thick. 

 Spikelets with 1-4 achenes. 



Rachis wingless or narrowly winged. 



Umbel simple or head solitary : leaf-blades relatively narrow. 

 Spikelets loosely spicate. 

 Spikelets densely spicate or capitate. 

 Heads ovoid to cylindric. 

 Heads globose to subglobose. 



Heads dark brown : scales mucronulate. 

 Heads green or greenish brown : scales not mu- 

 cronulate. 



Achene 2 mm. long : scales about 2 mm. long. 

 Achene 1 mm. long : scales less than 2 mm. 



long. 



Umbel compound : leaf-blades relatively broad. 

 Rachis- wings broad, membranous. 

 Scales firm, not appressed. 

 Scales thin, closely appressed. 

 Spikelets with 5-10 achenes. 



Heads sessile, or on rays less than 2 cm. long. 

 Heads terminating rays 2-7 cm. long. 



63. C. tetragonus. 



64. C.flavus. 



65. C. fuligineus. 



66. C.flliculmis. 



67. C. Blodgettii. 



68. C. ligularis. 



69. (7. Grayi. 



70. C. echinatus. 



71. C. brunneus. 



72. C. Ottonis. 



1. Cyperus flavescens L. Annual, yellowish green. Leaf -blades 2-3 mm. wide, 

 smooth, the longer usually exceeding the inflorescence : scapes very slender, tufted, 7-30 

 cm. tall : spikelets in 3's-6's, linear, subacute, yellow, many -flowered, flat, 8-18 mm. long, 

 3-4 mm. broad ; the clusters terminal and sessile, or on 1-4 short rays : scales ovate, ob- 

 tuse, 1-nerved, appressed, twice as long as the achene : stigmas 2 : achenes orbicular-obo- 

 void, black, obtuse, shining, the superficial cells oblong. 



In marshy soil, Maine to Michigan, Florida and Mexico. Also in the Old World. Summer and fall . 



2. Cyperus didndms Torr. Annual, deep green. Leaf-blades about 2 mm. wide : 

 scapes tufted, slender, 5-40 cm. tall : bracts of the involucre usually 3 : spikelets 8-18 

 mm. long, linear-oblong, acute, flat, many-flowered ; the clusters sessile and terminal or at 



