POACEAE. 35 



1-sided spikes or racemes; glumes unequal, hispid, mucronate; 

 sterile lemma similar and usually awned from the apex. 



Echinochloa crus-galli (L.) Beauv. Barnyard grass. Glabrous; stems 

 stout, branching at the base, 30-120 cm. tall; panicle dense, 10-20 cm. long, 

 composed of many ascending or spreading racemes; spikelets green or purple, 

 3 mm. long, densely crowded in 3 or 4 rows; sterile lemma awned or in some 

 forms awnless. 



Introduced from Europe, a weed in moist ground. 



48. CHAETOCHLOA. 



Annual grasses with erect stems and flat leaves ; spikelets with 

 one perfect flower and rarely also a staminate one, in spike-like 

 panicles; pedicels bearing bristles; glumes and lower lemma 

 membranous, the latter often containing a palea and rarely a 

 staminate flower; upper lemma papery with a similar palea and 

 a perfect flower. 



Chaetochloa viridis (L.) Scribn. Green Foxtail. Annual, usually tufted, 

 green; stems 30-90 cm. high; leaf-blades flat, 4-10 mm. wide, scabrous on the 

 margins; spikes green, 3-5 cm. long, the rachis villous; bristles 1-3, upwardly 

 barbed, 6-12 mm. long; spikelets 2 mm. long; fertile lemma faintly wrinkled. 



Sparingly introduced. 



49. PASPALTJM. 



Perennials with 1-flowered spikelets in 2 rows along one side 

 of a rachis forming racemes; lower glume usually wanting; 

 lemma hard and firm, its margin inrolled; palea firm; grain 

 oblong, inclosed within the hardened glume and palea. 



Paspalum distichum L. Stems ascending from a creeping base; leaves 4— 

 12 cm. long; spikes in terminal pairs, 2-5 cm. long; spikelets acute, 2.5-3 mm. 

 long. 



On overflowed river banks, especially along the Columbia River; probably 

 introduced. 



50. PANICUM. 



Spikelets with one perfect flower, often with a staminate 

 one below it; glumes 2, membranous; lemmas 2, the lower empty 

 or including the staminate flower, the upper indurated, shining, 

 enclosing a similar palea and the perfect flower; awns none 

 (in ours) ; fruit a caryocist, the free grain enclosed in a box formed 

 by the hardened lemma and palea. 



Annual; panicle very long-rayed; spikelets acute. P. barbipuhinatum. 



Perennial; panicle rather short-rayed. 



Basal leaves like the stem leaves ; spikelets acute. P. agrostoid.es. 



Basal leaves different from the stem leaves, usually 

 forming a rosette; spikelets obtuse. 

 Spikelets 3 mm. long, glabrous or nearly so. P. scribnerianum. 



Spikelets 2 mm. long, pubescent. 



Leaves glabrous on upper surface. P. occidentale. 



Leaves pubescent on upper surface. P. pacificum. 



