GRAMINEAE (GRASS FAMILY) 



39 



as follows : The two empty glumes are merely the glumes; the flowering glume 

 is the lemma; the additional glume in the Paniceae (the so-called third glume) 

 is the sterile lemma; palet and lodicule are used as heretofore. 



Key to the Tribes * 



Spikelets falling from the pedicels entire, naked or inclosed in 



bristles or bur-like involucres, 1-flowered, or if 2-flowered 



the lower flower staminate; no upper empty lemmas; ra- 



chilla not extending above the sterile lemma. 



Spikelets round or somewhat compressed dorsally; glumes 



manifest; hilum punctiform. 

 Lemma and palet hyaline, thin, much more delicate in 



texture than the glumes. 



Spikelets in pairs, one sessile and the other pedicellate 

 Spikelets not in pairs (Alopecurus, Polypogon, Cinna, 



etc.) 



Lemma, at least that of the perfect flower, similar in tex- 

 ture to the glumes, or thicker and firmer, never hya- 

 line and thin. 



Lemma and palet membranous; the first glume usually 

 larger than the rest ...... 



Lemma and palet chartaceous to coriaceous, very dif- 

 ferent in color and appearance from the glumes. 

 Spikelets much compressed laterally; glumes none or rudi- 

 mentary; hilum linear 



Spikelets with the glumes persistent, the rachilla articulated 



above them, 1-many-flowered; frequently the upper 



lemmas are empty; rachilla often produced beyond the 



sterile lemma. 



Spikelets borne in an open or spike-like panicle or raceme, 



usually upon distinct pedicels. 

 Spikelets 1-flowered. 



Glumes 4; palet 1-nerved ..... 



Glumes 2, rarely 1; palet 2-nerved (except in Cinna) 

 Spikelets 2-many-flowered. 



Lemma usually shorter than the glumes; the awn 



dorsal and usually bent 



Lemma usually longer than the glumes; the awn termi- 

 nal and straight (rarely dorsal in Bromus) or none 

 Spikelets in two rows, sessile or nearly so. 



Spikelets on one side of the continuous axis, forming one- 

 sided spikes ........ 



Spikelets alternately on opposite sides of the axis, which 

 is often articulated . .... 



Tribe I. Andropogoneae. 



Tribe VI. Agrostideae. 



Tribe II. Zoysieae. 



Tribe HI. Paniceae. 



Tribe IV. Oryzeae. 



Tribe V. Phalarideae. 

 Tribe VI. Agrostideae. 



Tribe VII. Aveneae. 



Tribe IX. Festuceae. 



Tribe VIH. Chlorideae. 



Tribe X. Hordeae. 



Tribe I. ANDROPOGONEAE 



Rachis-internodes not sulcate; branches of the simple panicle paired, 



or rarely single or variously branched. 

 Some or all of the racemes sessile ...... 1. Andropogon. 



All of the racemes more or less peduncled. 



Pedicellate spikelets wanting .3. Sorghastrum. 



Pedicellate spikelets present and usually staminate . . 4. Sorghum. 

 Rachis-internodes sulcate ........ 2. Amphilophis. 



Tribe H. ZOYSIEAE 

 Inflorescence in terminal spikes ....... 6. Hilaria. 



* This excellent key to the tribes represented in our range is taken without change (except 

 in terms used) from Rydberg's Flora of Colorado. The generic keys have been adapted 

 from those of Rydberg's Fl. Colo.; Piper's Fl. Wash.; and Britton's Man. 



