FESTUCEAE 129 



56 ERIONEURON Nash. 



I. Erioneuron pilOSUm (Huckl.l Nash. A not uncommon lit- 

 tle grass of the liiiilur mesas cf the SDUllu'rn and eastern ^jart 

 of the State: m(i>tly in the I'pi.cr SoiiM-an Zone. 



57. TRIDENS U. and S. 



Flowering glumes not pilose on the back; 

 empty glumes considerably surpassing the 



lower flowers of the spikelet. 1. T. albescens. 



Flowering glumes piloHc on tlie back at least 

 at the base. lOmpty glumes smaller, bare- 

 ly as long us the lowest flowers or shorter. 

 First flowe; ing glume stiongly ciliate, deep- 

 ly 2-l()bed with an intermediate short 

 awn. 

 Floweiing glumes orly slightly 2-cleft at 

 the apex sometimes hardly at all so; 



lobes if present narrow, acute. -. T. (jrcnidiflorus. 



Flowering glumes cleft 1-2 of their length; 



lobes rounded obtuse. 3. T. ncalleyi. 



First flowe-ing glume not ciliate, nor lobed 



and without any awn. 1. V. muticus. 



1. Tridens albescens (Vasey). in the valieys at the 



southern ei'd oi' the Slate: in the Lower Sonoran Zone. 



2. Tridens grandiflorus (Vasey). A single specimen is 

 in the luil;arir,m fidin near Kingston. It probably occurs occas- 

 ional'y in the mountaiis of the sdutliern i^art of the State. 



3. Tridens nealleyi (Vnseyl. A rather rare grass in the 

 Lower Soi:oran Zone. 



4. Tridens muticus (Torr.) Xash. At the lower levels on 

 mesas a.rd in the \ alleys, in the T^ower Sonoran Zone. 



58. KOELERIA Peis. JrxE Grass 



I. K^eleria cristata (L. ) Pers. One of the comn.onest 

 and most attractive h)oking grasses of the timbered areas of the 

 State: in the Trar.sition Z-^oe. sometimes reaching into the Canadian 

 Zone. 



