GENERA OF GRASSES OF THE UNITED STATES. 167 



80. HILAEIA H. B. K. 



Spikelets sessile, in groups of 3, the groups falling from the 

 axis entire, the central spikelet (next the axis) fertile, 1-flowered, the 

 2 lateral spikelets staminate, 2-flowered ; glumes coriaceous, those of 

 the 3 spikelets forming a false involucre, in some species connate 

 at the base, more or less asymmetric, usually bearing an awn on 



FIG. 97. Manila grass, Osterdamia matrella. Plant, X I ; spikelet, X 10 ; floret with 

 caryopsis, the palea obsolete, X 10. 



one side from about the middle; lemma and palea hyaline, about 

 equal in length. 



Perennial low grasses, the groups of spikelets appressed to the 

 axis, in terminal spikes. Species five, in arid regions, southwestern 

 United States to Central America, all but one found within the limits 

 of the United States. 



Type species: Hilaria cenchroides H. B. K. 



Hilaria H. B. K., Nov. Gen. and Sp. 1 : 116. 1816. Only one species described. 



