20 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



Glumes not papery; upper florets not unlike the others. 

 Nerves of lemma parallel, not converging at summit or 



but slightly so. 

 Spikelets in racemes. 



Racemes short, dense, overtopped by the leaves; 



spikelets awnless 7. SCLEROCHLOA. 



Racemes elongate, loose, exserted;spikelets a wned 



or mucronate. 9. PLEUROPOGON. 



Spikelets in open or contracted panicles. 



Nerves prominent; plants usually rather tall, 

 growing in woods or fresh-water marshes. 



6. GLYCERIA. 

 Nerves faint; plants low, growing in saline soil. 



5. PUCCINELLIA. 



Nerves of lemma converging toward summit, the 



lemmas narrowed at apex. 



Lemmas awned or awn-tipped from a minutely 

 bifid apex (awnless in B. brizaeformis} . 



2. BROMUS. 



Lemmas entire, pointed, awnless or awned from 

 the tip (minutely toothed in Festuca elmeri and 

 F. gigantea). 

 Spikelets awned (awnless in a few perennial 



species) ; lemmas pointed 3. FESTUCA. 



Spikelets awnless. 



Second glume 5- to 9-nerved; spikelets mostly 

 1 cm or more long; lemmas broad, many- 

 nerved, firm 30. VASEYOCHLOA. 



Second glume 1- to 3-nerved; spikelets smaller; 

 lemmas 5-nerved, membranaceous, not 

 pointed. 

 Spikelets on slender pedicels in compound 



panicles; perennials 10. POA. 



Spikelets on thick short pedicels in simple 

 panicles; annual 4. SCLEROPOA 



TRIBE 3. HORDEAE 



Spikelets 1- to several-flowered, sessile on opposite sides of a jointed 

 or continuous axis forming symmetrical spikes (not one-sided, but 

 spikelets sometimes turned to one side in some species). 



This small but important tribe, found in the temperate regions of 

 both hemispheres, includes our most important cereals, wheat, barley, 

 and rye. The rachis is flattened or concave next to the spikelets, or 

 in some genera is thickened and hollowed put, the spikelets being 

 more or less enclosed in the hollows. In Triticum and its allies there is 

 one spikelet at each node of the rachis ; in Hordeum and its allies there 

 are 2 or 3 at each node. In Lolium and its allies the spikelets are 

 placed edgewise to the rachis, and the first or inner glume is suppressed 

 except in the terminal spikelet. The rachis of the spikes disar- 

 ticulates at maturity in several genera. In some species of Elymus 

 and especially in Sitanion the glumes are very slender, extending into 

 long awns, in the latter genus sometimes divided into several slender 

 bristles. The spikes are rarely branched or compound, especially 

 in Elymus condensatus. In this tribe the blades of the leaves bear on 

 each side at the base a small appendage or auricle. 



Key to the genera of Hordeae 



la. Spikelets solitary at each node of the rachis (rarely 2 in species of Agropyron, 



but never throughout) . 



2a. Spikelets 1-flowered, sunken in hollows in the rachis. Spikes slender, 

 cylindric; low annuals. 



