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



lower branches of the panicle; plants annual or perennial 121. Zizania. 



Pistillate spikelets at the ends, the staminate below on the same branches of the panicle; 

 plants perennial 122. Zizaxiopsis. 



TRIBE 11. MELINIDEAE 



Spikelets disarticulating below the glumes, these very unequal, the first 

 minute, the second and the sterile lemma equal, membranaceous, strongly 

 nerved, the latter bearing a slender awn from the notched summit; fertile 

 lemma and palea thinner in texture, awnless. 



A tribe of about a dozen genera represented in the United States by an in- 

 troduced species, Melinis minutiflora. 



TRIBE 12. PANICEAE 



Spikelets with 1 perfect terminal floret and below this a sterile floret and 

 2 glumes; fertile lemma and palea indurate or at least firmer than the glumes 

 and sterile lemma, a lunate line of thinner texture at the back just above the 

 base, the rootlet protruding through this at germination; articulation below 

 the spikelet. 



A large tribe, confined mostly to warm regions, and containing relatively 

 few economic species. The first glume is wanting in some genera, such as 

 Paspalum, and rarely the second glume also (Reimarochloa) , The spikelets 

 are usually awnless, but the glumes and sterile lemma are awned in Echinochloa 

 and Oplismenus, and the second glume and sterile lemma in Rhynchelytrum. 

 In Eriochloa and in some species of Brachiaria the fertile lemma is awn-tipped. 

 In Setaria there are, beneath the spikelet, 1 or more bristles, these repre- 

 senting sterile branchlets. In Pennisetum similar bristles form an involucre, 

 falling with the spikelet. In Cenchrus the bristles are united, forming a bur. 

 The spikelets are of 2 kinds in Amphicarpum, aerial and subterranean. The 

 culms are woody and perennial in Lasiacis and Olyra. 



Key to the genera of Paniceae 

 Spikelets of two kinds. 



Spikelets all perfect, but those of the aerial panicle rarely perfecting grains, the fruitful 



spikelets borne on subterranean branches 146. Amphicaepum. 



Spikelets unisexual, the pistillate above, the staminate below on the branches of the same 



panicle. Blades broad, elliptic 147. Olyra. 



Spikelets all of one kind. 



Spikelets sunken in the cavities of the flattened corky rachis 131. Stenotaphrum. 



Spikelets not sunken in the rachis. 



la. Spikelets subtended or surrounded by 1 to many distinct or more or less connate 

 bristles, forming an involucre. 



Bristles persistent, the spikelets deciduous - 143. Setaria. 



Bristles falling with the spikelets at maturity. 



Bristles not united at base, slender, often plumose 144. Pennisetum. 



Bristles united into a burlike involucre, the bristles retrorsely barbed. 



145. Cenchrus. 

 lb. Spikelets not subtended by bristles. 



Glumes or sterile lemma awned (awn short and concealed in the silky hairs of the 

 spikelet in Rhynchelytrum; awn reduced to a point in Echmochloa colonum). 



Inflorescence paniculate; spikelets silky 142. Rhynchelytrum. 



Inflorescence of unilateral simple or somewhat compound racemes along a common 

 axis ; spikelets smooth or hispid, not silky. 



Blades lanceolate, broad, thin; culms creeping 140. Oplismenus. 



Blades long, narrow; culms not creeping 141. Echinochloa. 



Glumes and sterile lemma awnless. 



2a. Fruit cartilaginous-indurate, flexible, usually dark-colored, the lemma with 

 more or less prominent white hyaline margins, these not inrolled. 

 Spikelets covered with long silky hairs, arranged in racemes, these panicled. 



128. Trichachne. 

 Spikelets glabrous or variously pubescent but not long-silky (somewhat silky in 

 Digitaria villosa). 



