22 POACEAE. 



Tribe 2. PANICEAE. Millet Tribe. 



Spikelets hermaphrodite, terete or flattened on the 

 back. Glumes 3-4, rarely 2, when 4 the third usually 

 includes a staminate flower in its axil; flowering glume 

 firmer in texture than the outer ones. Axis of the in- 

 florescence not articulated, the rachilla being articulated 

 below the empty glumes and the spikelets falling off 

 singly from the pedicels. 



Spikelets not surrounded by a bristly or spiny in- 

 volucre. 

 Glumes 3; spikelets sessile or on short pedicels 



in unilateral spikes or racemes. 3, Paspalum. 



Glumes 4, the first usually short, rarely wanting. 



Spikes digitate. 4. Digitaria. 



Spikes not digitate. ^ ^ 5. Panicum. 



Spikelets surrounded by a bristly or spiny involucre. 



Bristles slender, not falling with the spikelets. 6. Setaria. 

 Bristles thickened below, spine-like, falling with 



the spikelets. 7. Cenchrus. 



3. PASPALUM L. Ditch-grass. 



Perennial grasses of various habit, with generally flat 

 leaves and 1 -flowered spikelets borne in 2-4 rows on 1- 

 sided spikes, which are single, in pairs or panicled. 

 Spikelets oblong to orbicular, flat on the inner surface, 

 convex on the outer. Glumes 3, rarely 2 by the absence 

 of the outermost, the outer ones membranous, the inner 

 one indurated and subtending a palea and perfect flower. 

 Stamens 3. Styles distinct; stigmas plumose. Ovary 

 oblong or ovoid, smooth. 



1. P. distichum L. Culms erect, 15-35 cm. high, creeping at the 

 base; sheaths smooth, sometimes ciliate on the rnargins or sparsely 

 pubescent; leaves flat, 4-10 cm. long, 2-4 mm. wide, smooth; spikes 

 25-50 mm. long, in pairs, or occasionally with a third, exserted; 

 rachis fiat, 1-2 mm. wide, smooth; spikelets 2.5-3 mm. long, elliptic, 

 somewhat pubescent or glabrous, acute, nearly sessile in 2 rows; 

 outer glumes 3-5-nerved, slightly exceeding the acute third one, 

 which is sparingly bearded at the apex. 



Frequent along streams and irrigating ditches. Los Angeles; 

 Santa Ana. 



4. DIGITARIA Scop. Crab-grass. 



Annual grasses with flat leaves. Spikelets borne in 

 pairs or in 3's in secund spikes which are digitate or 



