158 MISC. PUBLICATION 4 2 3, U. S. DEPT. OF AGRICULTURE 



11. Plant not stoloniferous; flowering stems often bulbous-thickened at 



base or arising from rootstocks (15). 



15. Flowering stems not bulbous-thickened at base; plant annual (16). 



16. Scales less than 1 mm. long, orbicular-obovate, rounded at apex; 



stamens 1 or 2 ; achene nearly as long as the scale ; inflorescence 



often appearing lateral, the longest bract of the involucre more 



or less erect 5. C. difformis. 



16. Scales not less than 1 mm. long, lanceolate or ovate-lanceolate, 

 acutish or mucronulate at apex; stamens 3; achene about half as 

 long as the scale; inflorescence not appearing lateral (17). 

 17. Spikes elongate, the rachis much longer than the spikelets, the 

 latter seldom more than 10 mm. long; scales not more than 

 1.5 mm. long, 3-nerved, the sides becoming gold- or copper- 

 colored 1. C. ERYTHRORHIZOS. 



17. Spikes very short, the rachis shorter than the spikelets, the 

 latter usually more than 10 mm. long; scales 2 to 3.5 mm. 

 long, 7- to 9-nerved, the sides becoming red or mahogany- 

 colored; inflorescence often umbelliform__ 11. C. PARISHII. 

 15. Flowering stems bulbous-thickened at base, often arising from a 

 rootstock, this usually very short; plant perennial (18). 

 18. Inflorescence normally contracted, the spikes sessile or borne on 

 ravs not more than 1 cm. long; spikelets with onlv 1 to 3 fertile 

 flowers (19). 

 19. Lateral nerves of the scales inconspicuous or obsolete; spikelets 

 4 to 5 mm. long; achene ovate-oblong in outline. 



19. C. SUBAMBIGUUS. 



19. Lateral nerves of the scales conspicuous; spikelets 3 mm. long; 



achene ovate or obovate in outline 20. C. flavus. 



18. Inflorescence normally expanded, with some of the rays at least 

 2 cm. long; spikelets with 1 to several fertile flowers (20). 



20. Scales usually about twice as long as the achene, greenish or pale 



brown on the sides; stems usually stout; spikes cylindric; 



fertile flowers 2 or more 16. C. pringlei. 



20. Scales considerably less than twice as long as the achene; stems 

 slender; spikes broadly ovoid or subglobose; spikelets slender, 

 acuminate; fertile flowers 1 or 2 18. C. uniflorus. 



1. Cyperus erythrorhizos Muhl., Gram. 20. 1817. 



Picacho Lake, Pinal County, 1,600 feet {Taylor in 1934), also col- 

 lected at Fort Yuma, Calif., on the western bank of the Colorado 

 River, 140 feet. Massachusetts to Florida, west to California. 



The form occurring in Arizona may be var. cupreus (Presl) 

 Ktikenthal. 



2. Cyperus rotundus L., Sp. PL 45. 1753. 



Salt and Gila River Valleys (Pinal, Maricopa, and Yuma Counties). 

 Widely distributed in tropical and subtropical America, presumably 

 of Old World origin. 



Nutgrass. A common and troublesome weed in irrigated lands. 



3. Cyperus esculentus L., Sp. PI. 45. 1753. 



Central and southern Arizona (Navajo and Yavapai Counties to 

 Cochise, Santa Cruz, Pima, and probably Yuma Counties), up to 

 5,000 feet. Widely distributed in America, as far north as Ontario 

 and Alaska; Eastern Hemisphere. 



Chufa, yellow nutgrass. Common in wet soil, often a weed in 

 cultivated fields and pastures. A form with exceptionally short 

 rachis and long spikelets, var. leptostachyus Boeckl., was collected 

 near Scottsdale, Maricopa County (Peebles 14420), and in Bab o qui var i 

 Canyon, Pima County (Gilman A26). 



