300 POACExE. 



or rarely in pairs, the lower 4-6 cm. long, the lower two-fifths 

 naked. Spikelets somewhat crowded, on sliort unequal pedicels, 1 

 mm. long; second glume nerveless, about 0.5 mm. long, obtuse, 

 broader and a little longer than the first; floral glume and palea 

 equal, obtuse, nerveless. Nearly allied to S. atrovirens Kunth. 

 See notes by Prof. Scribner in Phil. Acad. Sci., p. 299. 1891. 



Mexico, Pringle 3130. 



Thin soil of limestone ledges, San Luis Potosi, Mexico. 



30. S. racemosus Vasey, Bull. Torr. Club, 15:9 (1888). 



A slender erect or decumbent freely branching annual, 18-35 

 cm. high. Sheaths loose, shorter than the internodes; ligule less 

 than 0.5 mm. long; blades 4-7 in number, thin, flat or involute, 

 2-4 cm. long, 1 mm. wide or less. Panicles terminal and lateral, 

 the former exserted, the latter more or less included, open, 4-8 

 cm. long, rays mostly single, simple, the longest 2-3 cm. long and 

 few-flowered. Spikelets racemose on short, slender, glandular 

 pedicels; empty glumes broad and obtuse, usually nearly equal, not 

 over 0.5 mm. long; floral glume and palea ovate, smooth, nerves 

 obscure, about 1 mm. long. Anthers 3, red, 1.8 mm. long, 1.8 

 mm. wide, very exceptional in the genus. So far as observed, the 

 anthers of all other species have been linear. The plants through- 

 out tinged with red. 



Mexico (Chihuahua), Pringle 1425. 



Cool, gravelly slopes, near water. 



'M. S. ovatus. S. minor Vasey, A. Gray Man. Ed. : 646 

 (1890). 



A slender geniculate scabrous perennial, 10-30 cm. high. 

 Sheaths half as long as the internodes; ligule very short near it 

 and above and below are scanty hairs with warty bases; blades in- 

 volute, those from sterile shoots 1-4 cm. long, those of the culm 3-5 

 in number, and 2-5 cm. long, 1.5-2 mm. wide. Panicle scarcely 

 exserted, very simple, 1-4 cm. long, 3-4 mm. wide; empty glumes 

 nearly equal, ovate-lanceolate, 1-nerved, keeled toward the apex, 

 about 3 mm. long; floret clothed with very short hairs as seen under 

 a lens; floral glume ovate, acute, somewhat compressed toward the 

 apex, 1-nerved, 2.7 mm. long; palea as long as and as wide as its 



