lauca.=

6b. Bristles 1-3 at the base of each spikelet --7.

7a. Spikelets about 2 mm. long; bristles not much longer, green
=Green Foxtail, Setaria viridis.=

7b. Spikelets about 3 mm. long; bristles much longer, usually purple
=Millet, Setaria italica.=

8a. Spikelets numerous, in long slender symmetrical spikes --9.

8b. Spikelets in panicles, racemes, or loose spikes --13.

9a. Spikelets without awns; plants 8 dm. high or less (Crab Grass) --10.

9b. Spikelets with awns; plants 12 dm. high or more --12.

10a. Leaf-sheaths all glabrous. =Crab Grass, Digitaria humifusa.=

10b. Lower leaf-sheaths hairy --11.

11a. Axis of the spike flat, with wing-like margins
=Crab Grass, Digitaria sanguinalis.=

11b. Axis of the spike slender, without winged margins
=Crab Grass, Digitaria filiformis.=

12a. Spikes numerous, appressed to the axis of the panicle; tall
marsh grass =Slough Grass, Spartina michauxiana.=

12b. Spikes 2-6, widely divergent; plant of dry ground
=Blue-joint, Andropogon furcatus.=

13a. Spikelets subtended by an ovoid thorny involucre 3-8 mm. wide
=Sand Bur, Cenchrus carolinianus.=

13b. Spikelets without a thorny involucre --14.

14a. Lower branches of the panicle spreading, bearing staminate
flowers, the upper branches erect, with pistillate flowers;
aquatic or marsh grass 2-4 m. high
=Wild Rice, Zizania aquatica.=

14b. Panicle uniform throughout --15.

15a. Spikelets with awns 2 mm. or more long --16.

15b. Spikelets not awned, or with short inconspicuous awns --18.

16a. Spikelets in solitary raceme-like spikes; awn about 1 cm. long
or more =Beard Grass, Andropogon scoparius.=

16b. Spikelets in branching clusters; awn less than 1 cm. long
--17.

17a. Leaf-blade 4 mm. wide or narrower; panicle slender
=Drop-seed, Muhlenbergia schreberi.=

17b. Leaf-blade 6 mm. wide or more; panicle stout and coarse
=Barnyard Grass, Echinochloa crus-galli.=

18a. Spikelet plump and compact, its bracts closely folded about