194 BULLETIN 772, U. S. DEPARTMENT OF AGRICULTURE. 
Three species are annuals, B. aristidoides 'Thurb., B. procumbens 
(Durand) Griffiths (B. prostrata Lag.), and B. barbata 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- 
494, 1912. Economic notes 
and synonymy are included. 
96. CATHESTECUM Presl. 
Spikes consisting of 3 
spikelets, the upper or cen- 
tral perfect, the 2 lateral 
staminate 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 3; 
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 
