370 



CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



DESCRIPTION. 



A smooth, cespitose, half-prostrate or spreading perennial; culms ascending, seldom 

 geniculate or branched, 20 to 30 cm. long; sheaths striate, smooth, close; blades nar- 

 row, involute, short, only 4 or 5 cm. long, with a narrow ligular fringe of white hairs; 



spike always solitary and terminal, 4 to 5 cm. long, revolute 



toward maturity; spikelets 50 to 70, pectinate, about 6 mm. 



long, consisting of 



a lower floret and 



an upper rudiment ; 



glumes smooth, not 



sharply keeled, 



rounded to abrupt- 

 ly pointed, awn- 

 less, the lower 3.3 



mm., the upper 5.3 



mm. long; lemma 



densely hairy, 5.5 



mm. long, with 3 



equal awns and 4 



lobes, the two cen- 



tral lobes being 



nearly as long as' 



the awns, the lat- 

 eral lobes short and 



attached nearly the 



entire length to the 



lateral awns; palet 



as long as the lem- 

 ma, truncate, awnless; rudiment 5.5 mm. 

 long, hairy-tufted, with 3 equal scabrous 

 awns and 2 axillary scales representing the 

 lobes of the lemma; caryopsis not seen. 

 (Figures 31, 32.) 



This species is as uniformly 1-spiked as 

 is B. procumbens. In other respects the 

 herbarium material bears a close similarity 

 to some single-spiked forms of B. gracilis. 

 On the whole, however, the plants as well 

 as the glumes are smoother and the spikes 

 are longer, heavier, and more revolute. In 

 the field the difference is still more strik- 

 ing. In this species the larger plants grow 

 in more conspicuous bunches and are more 

 spreading, and the general aspect, owing fig. 32.— Bouteloua scorpioides. a, Spike; b, spike- 

 to this fact and the lack of pubescence, is let; c, d, lemma and palet of first floret; e, rudi- 

 entirely different. One-spiked forms of B. 

 gracilis are not at all uncommon. Such 

 forms might easily be confused with B. scorpioides by one who had never seen the 

 latter in the field. The range of B. scorpioides, however, is apparently limited to the 

 high plateau of central Mexico. One-spiked forms that have been examined from 

 northern Mexico or the United States can not be referred to this species. 



When Pringle's no. 8820, from Zontecomate Station, Hidalgo, Mexico, was first 

 seen it was thought that it was a distinct species. Pittier's no. 422, from the State of 



Fig. 31.— Bouteloua scorpio- 

 ides. a, Spikelet; b, c, lem- 

 ma and palet of first floret ; 

 d, e, rudimentary lemma 

 and palet of second floret; 

 /, rudiment of third floret, 

 o, Scale 5; b-f, scale 7.5. 

 From Pringle 8820. 



ment. a, Scale 1; 6, scale 5; c-e, scale 10. 



Griffiths 8527. 



From 



