ELODIACEAE. 15 



Order 12. HYDROCHARITALES. 

 Family 17. ELODIACEAE Dumort. TAPE-GRASS FAMILY. 



i. PHILOTRIA Raf. WATER-WEED. 



Calyx over 2.5 mm. broad. i. P. angustifolia. 



Calyx less than 2 mm. broad. 2. P. minor. 



1. Philotria angustifolia (Muhl.) Britton. In ponds and slow-flowing water 

 from N. Y. to Sask., Ky. and Nev. Alt. 4000-6500 ft. Lee's Lake, Ft. 

 Collins. 



2. Philotria minor (Engelm.) Small. In ponds and slow-flowing streams 

 from Me. to Minn., Wyo., Tenn. and Colo. Alt. 4000-6000 ft. Rio Grande; 

 Alamosa; Lee's Lake. 



Order 13. POALES. 



Leaves 2-ranked ; their sheath with their margins not united ; stem mostly hollow ; 



fruit a grain. Fam. 18. POACEAE. 



Leaves 3-ranked ; their sheath with united margins ; stem solid ; fruit an achene. 



Fam. 19. CYPERACEAE. 



Family 18. POACEAE R. Br. GRASS FAMILY. 



Spikelets falling from the pedicles entire, naked or enclosed in bristles or bur- 

 like involucres, i -flowered, or if 2-flowered the lower flower staminate ; no 

 upper empty glumes ; rachilla not extending above the upper glume. 

 Spikelets round or somewhat compressed dorsally ; empty glumes manifest ; 



hilum punctiform. 

 Flowering glume and palet hyaline, thin, much more delicate in texture than 



the empty glumes. 

 Spikelets in pairs, one sessile and the other pedicellate. 



Tribe i. ANDROPOGONEAE. 

 Spikelets not in pairs (Alopecurus, Polypogon, Cinna, etc.). 



Tribe 6. AGROSTIDEAE. 

 Flowering glume, at least that of the perfect flower, similar in texture to the 



empty glumes, or thicker and firmer, never hyaline and thin. 

 Flowering glume and palet membranous ; the first glume usually larger than 



the rest. Tribe 2. ZOYSIEAE. 



Flowering glume and palet chartaceous to coriaceous, very different in color 



and appearance from the remaining glumes. Tribe 3. PANICEAE. 

 Spikelets much compressed laterally ; empty glumes none or rudimentary ; hilum 



linear. Tribe 4. ORYZEAE. 



Spikelets with the empty glumes persistent, the rachilla articulated above them, 

 i -many-flowered ; frequently the upper glumes are empty ; rachilla often pro- 

 duced beyond the upper glume. 



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

 tinct pedicels. 

 Spikelets i -flowered. 



Empty glumes 4 ; palet i-nerved. Tribe 5. PHALARIDEAE. 



Empty glumes 2, rarely i ; palet 2-nerved (except in Cinna). 



Tribe 6. AGROSTIDEAE. 

 Spikelets 2-many-flowered. 



Flowering glumes usually shorter than the empty glumes ; the awn dorsal 



and usually bent. Tribe 7. AVENEAE. 



Flowering glumes usually longer than the empty ones ; the awn terminal 

 and straight (rarely dorsal in Bromus) or none. 



Tribe 9. FESTUCEAE. 



