FLOWERING PLANTS AND FERNS OF ARIZONA 153 



a tightly twisted, once-geniculate awn; pedicellate spikelet wanting, 

 only the hairy pedicel present. 



1. Sorghastrum nutans (L.) Nash in Small, Fl. Southeast, U. S. 66. 

 1903. 



Andropogon nutans L., Sp. PL 1045. 1753. 



Apache, Navajo, Coconino, and Cochise Counties, at medium alti- 

 tudes, dry slopes and canyons, August to October. Quebec and 

 Maine to Manitoba and North Dakota, south to Florida, Arizona, 

 and Mexico. 



Tins grass affords fairly good forage. 



77. HETEROPOGON. Tanglehead 



Annuals or perennials, with flat leaf blades and solitary terminal 

 racemes; lower few pairs of spikelets alike, staminate, awnless, the 

 remaining sessile spikelets fertile, long-awned, the pedicellate spikelets 

 staminate like the lower ones; rachis continuous below, bearing the 

 fertile spikelets above, disarticulating at base of each joint, the joint 

 forming a sharp, barbed callus below the fertile spikelet; glumes of 

 the fertile spikelet dark brown, coriaceous, the first glume enclosing 

 the second one; glumes of the staminate spikelet membranaceous, 

 broad, obscuring the fertile spikelets; lemmas hyaline, the fertile one 

 with a long, stout, twisted, geniculate awn. 



The mature fruits of tanglehead are injurious to sheep, but in the 

 young stage the plants make good forage. Sweet tanglehead (H. 

 melanocarpus) owes its common name to the fragrance of the fresh 

 foliage. 



Key to the species 



1 . Plant annual ; culms usually more than 1 meter high ; first glume of the staminate 

 spikelet with a row of conspicuous glands on the back. 



1. H. MELANOCARPUS. 



1. Plant perennial; culms slender, usually less than 1 meter high; first glume of the 

 staminate spikelet glandless, papillose-hispid 2. H. contortus. 



1. Heteropogon melanocarpus (Ell.) Benth., Linn. Soc. London Jour. 



Bot. 19: 71. 1881. 



Andropogon melanocarpus Ell., Bot. S. C. and Ga. 1: 146. 1816. 



Santa Cruz and Pima Counties, fields and waste places. Georgia, 

 Florida, Alabama, and Arizona; tropical and semitropical regions of 

 both hemispheres. 



2. Heteropogon contortus (L.) Beauv. in Roem. and Schult., Syst. Veg. 



2: 836. 1817. 



Andropogon contortus L., Sp. PL 1045. 1753. 



Mohave, Yavapai, Pinal, Cochise, Santa Cruz, and Pima Counties, 

 1,000 to 5,000 feet, rocky slopes and canyons, September to October, 

 occasionally January to April. Texas to Arizona; wanner regions of 

 both hemispheres. 



78. TRACHYPOGON. Crinkle-awn 



Densely tufted perennial with flat or subinvoluie leaf blades and 

 solitary terminal racemes; spikelets in pairs on a continuous rachis, 

 the sessile one staminate, awnless, persistent, the pedicellate spikelet 



