HOW TO KNOW THE GRASSES 



17a. First glume lacking or rudimentary, less than 1/10 as long as the 

 spikelet 18 



17b. First glume present, usually more than 1/3 as long as the spike- 

 let. Fig. 297. 



BrachiaTia platyphylla (Griseb.) Nash 



Annual; plants stooling out and sometimes 

 rooting at the lower nodes; culms 25 — 40 cm. 

 or more long; leaf blades thickish, 4 — 12 cm. 

 long, 6 — 12 mm. wide; rachis of the racemes 

 flattened, 1 — 2 mm. wide; spikelets glabrous 

 4 — 4.5 mm. long, the second glume and sterile 

 lemma prolonged beyond the end of the fer- 

 tile floret, forming a soft beak. Moist sandy 

 ground. Summer. Formerly known as B. 

 extensa. 



Brachiaria ciliatissima (Buckl.) Chase has 

 hairy foUage, and spikelets with woolly sec- 

 ond glume and sterile lemma. It makes 

 mats on dry sandy ground, the prostrate 

 culms rooting at the nodes. Texas, Okla- 

 homa, and Arkansas. 



18a. Fertile floret soft and flexible; margins of the lemma not rolled 

 in 19 



1 8b. Fertile floret hard and stiff; margins of lemma 

 rolled in 21 



19a. Rachis of the racemes thin and flat, with a pro- 

 nounced midrib. Fig. 298 20 



19b. Rachis of the racemes triangular in cross section. Figure 298 

 Fig. 299. 



Digitaria filifoTznis (L.) Koel. 



Figure 297 



Annual; tufted; culms erect, 10 — 60 cm. 

 tall; racemes 1 — 5, up to 10 cm. long. The 

 first glume is absent, and the equal second 

 glume and sterile lemma nearly cover the 

 chocolate brown fertile floret; spikelets 

 about 1.5 mm. long. Dry, usually sandy 

 disturbed soil. August — October. 



Figure 299 



157 



