120 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



32. Muhlenbergia arenicola Buckl., Acad. Nat. Sci. Phila. Proc 



1862: 91. 1862. 

 Mohave, Yavapai, Cochise, Pima, and Santa Cruz Counties, 4,000 

 to 7,000 feet, dry mesas and open ground, often forming "fairy rings," 

 August to October. Western Kansas and Colorado to Arizona and 

 northern Mexico. 



33. Muhlenbergia xerophila C. O. Goodding, Wash. Acad. Sci. 



Jour. 30: 19. 1940. 

 Pima and Santa Cruz Counties, canyons, September to November, 

 type from Sycamore Canyon near Kuby (L. N. Goodding M262). 

 Known only from southern Arizona. 



34. Muhlenbergia rigida (H. B. K.) Kunth, Rev. Gram. 1: 63. 1829. 



Podosaemum rigidum H. B. K., Nov. Gen. et Sp. 1: 129. 1815. 



Pima County, 5,000 to 6,000 feet, rocky slopes, September to 

 October. Texas, New Mexico, Arizona, and Mexico. 



35. Muhlenbergia emersleyi Vasey, Contrib. U. S. Natl. Herbarium 



3: 66. 1892. 



Muhlenbergia vaseyana Scribn., Mo. Bot. Gard. Ann. Rpt. 

 10: 52. 1899. 



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

 slopes and canyons at medium altitudes, July to October, type from 

 southern Arizona (Emersley). Texas to Arizona and Mexico. 



40. SPOROBOLUS. Dropseed 



Annuals or perennials with open or spikelike panicles of small 

 spikelets; glumes equal or (usually) unequal, the second often as long 

 as the lemma; lemma membranaceous, 1 -nerved, awnless; palea as 

 long as the lemma; fruit free from the lemma and palea. 



The perennial species are useful forage plants. Two large coarse 

 bunch grasses, alkali sacaton (S. airoides) and sacaton (S. wrightii), 

 are important elements of some Arizona ranges, but they are grazed 

 mainly when more succulent grasses are not available. Alkali sacaton 

 thrives on the plains and can withstand rather strongly saline soil 

 conditions. Sacaton reaches its highest development in the bottom 

 lands in the southeastern part of the State. Both species are utilized 

 for hay. Black dropseed (S. interruptus) , abundant on the plateau 

 south of Flagstaff and in the White Mountains, is one of the most 

 valuable forage grasses in its range. Sand dropseed (S. cryptandrus) 

 furnishes some forage. The seeds of several species have been used 

 for food by the Indians of Arizona. 



Key to the species 

 1. Plants annual (2). 



2. Panicles usually included in the sheaths, narrow, few-flowered, spikelike (3). 

 3. Spikelets 3 to 5 mm. long; lemma pubescent 1. S. vaginiflorus. 



3. Spikelets 2 to 3 mm. long; lemma glabrous 2. S. neglectus. 



2. Panicles exserted, open, many-flowered (4). 



4. Glumes glabrous; pedicels short, stiff, appressed along the main branches. 



3. S. RAMULOSTJS. 



4. Glumes pubescent, the pubescence sometimes sparse; pedicels slender, 

 spreading, club-shaped below the spikelets 4. S. microspermus. 



