GRIFFITHS THE GRAMA GEASSES. 413 



31. Bouteloua filiformis (Fourn.). 



Atheropogon filiformis Fourn. Mex. PL 2: 140. 1881. According to Fournier's de- 

 scription and a specimen cited by Foumier, Liebmann 585, this is a form with genicu- 

 late branching culms of what in this country has passed most commonly for B. bromoi- 

 des. Karwinski 991b and Liebmann 585 are in the St. Petersburg Botanical Garden, 

 and the latter number is also in the Berlin, Herbarium. The type, Karwinski 

 991b, has not been examined. 



Vasey a describes and figures this speoies under the name Bouteloua humboldtiana 

 Kunth. 



DESCRIPTION. 



An erect and cespitose or geniculate and spreading perennial, with branching 

 culms and with a more limited root system than B. radicosa; culms erect or spreading, 

 unbranched, 30 to 50 cm. high; sheaths smooth, striate, close; blades narrow, 1.5 to 2 

 mm. wide, delicate, with papillose hairs regularly distributed upon the margin; 

 ligule a ring of white hairs 1 mm. long or less; spikes commonly 8 mm. wide and 15 

 mm. long, but often 2 cm. long; spikelets about 10, not pectinate, 12 to 14 mm. long, 

 consisting of one perfect lower floret and an upper stamina te one; glumes strongly 

 hispidulously keeled, acuminate-pointed but not awned, nearly equal; lemma 

 about 7 mm. long, hispidulous on the nerves toward the apex, 3-nerved, 3-awned, 

 the lateral awns short and the central 1 mm. longer; palet as long as its lemma, toothed 

 but scarcely awned; rudiment consisting of a well-developed staminate floret with a 

 simple, undivided projection of the rachilla 1 mm. long extending above its insertion; 

 lemma of the staminate floret narrower and more conspicuously awned than that of 

 the lower floret, 7 to 8 mm. long over all, the central awn 1 to 2 mm. longer than the 

 lateral, its palet being about the same as that of the perfect floret; caryopsis about 4 

 mm. long and 1 mm. wide, the scutellum covering about three-fourths of the ventral 

 Burface. (Plates 82, A, 83.) 



The species is variable, especially in habit, and has an extensive range from Texas 

 to California and south into South America. In Arizona and the highland of northern 

 Mexico it is an erect plant.fr 



The typical form, that is, the form with geniculate culms growing in favorable 

 situations, is uncommon. There is a slight difference in leafage and color between 

 forms from the United States according as they grow in the deserts, or upon the 

 more fertile soils of southern Texas. In the latter situation, under cover of brush, the 

 whole plant becomes more lax and has a tendency to become geniculate in habit, like 

 the typical form of the species which is familiar to me in western Jalisco. 



The following, all from Mexico, appear to be typical of the species: Liebmann 585, 

 Consoquitla, and 575, valley of Oaxaca. Palmer 1254, Colima; 113, Acapulco; 482, 

 Tamaulipas. Botteri 107, Orizaba; Nelson, Atlixco, July 25 to August 1, 1903. 



HERBARIUM SPECIMENS. 



Arizona: Hitchcock 3499, Tucson; 3692, Patagonia. Griffiths 3441, 3386, Santa Rita 

 Forest Reserve; 1470, Rincon Mountains; 1949, Pearce. Griffiths & Thornber 3, 

 Santa Rita Forest Reserve. Lemmon 373. Mearns 931, south of Bisbee. Nealley 

 267, Monmouth. Rothrock 484, Camp Bowie. Davis 562, Clifton. Chase 5515, 

 Tucson. 



« U. S. Dept. Agr. Div. Bot. Bull. 12 1 : pi. 40. 1890. 

 b See discussion under Bouteloua americana. 



Explanation of Plate 82. — A, Bouteloua filiformis in lower foothills in southern Arizona upon stony 

 embankments, growing mainly with Lcptochloa dubia and B. curtipendula. B, Bouteloua curtipendula, 

 an uncommonly large bunch from near Greaterville, Arizona. 



Explanation of Plate 83. — a, Habit sketch of Bouteloua filiformis; b, spikelet; c, d, lemma and palet 

 of first floret; e,/, lemma and palet of second floret; g, two views of caryopsis; ft, portion of leaf blade, 

 a, One-fourth natural size; b-f, scale 5; y, scale 7.5; ft, scale 2.5. From Griffiths 7199. 



