388 



CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



geniculate at the very base; sheaths close, striate, smooth or very minutely roughened- 

 hispidulous, with ciliate-fringed ligule and minutely pubescent, hispid blades, bearing 

 a few long, scattered, papillose hairs, divaricate, 1 to 2 cm. (Letterman, Laredo, 1882) 

 to 3 to 7 cm. long (Griffiths 6338); panicle racemose, 4 to 7 cm. long, bearing 3 to 7 

 spikes, 1 to 1.3 cm. long, bearing about 12 pectinately arranged spikelets 7 to 8 mm. 

 long; spikelets consisting of one fertile floret and a rudiment; glumes about equal, 

 smooth, keeled, about3-5 mm. long; lemma hairy, 4 to 5 mm. long, bearing 3 scabrous 

 awns about 3 mm. long; palet 2-keeled, not awned, about 1.5 mm. long; rudiment 

 consisting of 3 hispid, equal awns, enlarged at base, about 4 mm. long, upon a naked 

 stipe 1 mm. long or less; caryopsis obovate, 0.8 mm. long, 0.3 mm. wide, the scutellum 

 somewhat oval, two-thirds the length of seed. (Plates 74, A; 78. Figures 41, 42.) 

 Like many other species of the genus this is very variable in size and general aspect. 

 The specimens marked type in the National Herbarium, as mentioned above, while 

 not the nomenclatorial types, are nevertheless typical of what was intended to be 

 published under these two names. For nomenclatorial purposes I consider them as 



Fig. 42. — Bouteloua trinii. a, Spikelet; 6, c, lemma and palet of first floret; d, rudiment; e, two views 

 and cross section of caryopsis. a, Scale 7.5; b-e, scale 15. a-d, From Letterman, Laredo, Tex. (typical of 

 B. burkii); e, from Griffiths 6338. 



good as types. Bouteloua burkii and Chondrosium trinii are the same form of plant; 

 that is, the shorter awned, more leafy plant, with longer, laxer leafage. 



Westward from about the region of Del Rio, Texas, the species is inclined to assume 

 a slightly different aspect. Especially is this true from the region of El Paso to Arizona. 

 The plant is somewhat dwarfed, the leaves are fewer, shorter, and more rigid, and the 

 awns slightly longer. In short, the same differences occur in this species upon 

 entering more arid situations as are found in B. gracilis in southern California where 

 the leaves become more radical, shorter, and more rigid, compared with those of more 

 humid sections. 



In the Rio Grande region the species is very important from the stockman's stand- 

 point, for it often constitutes the sum total of the forage upon the alluvial soils of the 

 shallow ravines and also extends onto the rocky knolls and ridges. 



When closely grazed it is short, with divaricate, crowded leaves near the base and 

 comparatively naked culms. When unmolested and consequently somewhat shaded 



Explanation of Plate 74.— -A. Bouteloua trinii as it grows in arid situations near Andrade, Arizona. 

 Here we always have the form described as B. trifida. B. An extraordinarily large bunch of Bouteloua 

 eriopoda from the Santa Rita Mountains, Arizona. 



