194 BULLETIN 772, U. S. DEPARTMENT OF AGRICULTURE. 



Three species are annuals, B. aristidoides Thurb., B. procumbens 

 (Durand) Griffiths (B. prostrata Lag.), and B. barbvta Lag. (B. 

 polystachya Torr.). These are found from Texas to Arizona, where 

 they are called six-weeks grama. They furnish forage when young, 

 but are of secondary importance. 



For a revision of the spe- 

 cies of Bouteloua and its 

 allies, see Griffiths, Contr. 

 U. S. Nat. Herb. 14:343- 

 424. 1912. Economic notes 

 and synonymy are included. 



96. CATHESTECUM Presl. 



Spikes consisting of 3 

 spikelets, the upper or cen- 

 tral perfect, the 2 lateral 

 stammate or rudimentary, 

 the spike falling entire; 

 central spikelet with one 

 perfect floret below and one 

 or more reduced florets 

 above; glumes unequal, the 

 first a short, thin, nerveless 

 scale in the central spikelet, 

 narrow and acuminate in 

 the lateral spikelets, the 

 second about as long as the 

 lemma, acuminate, all usu-" 



FIG. 114. Blue grama, Bouteloua gracilis. Plant, X 2 

 glumes, floret with rudiment, and floret alone, X 5. 



ally villous; lemma 3-nerved, or rarely 5 to 7 nerved, the nerves 

 extending into awns, and the internerves into teeth ; palea 2-nerved, 

 the nerves extending into short awns; second and third floret with 



