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



TRIBE 10. ZIZANIEAE 



Spikelets unisexual, the pistillate terete or nearly so; glumes 

 shorter than the lemma, usually one or both obsolete, the pedicel 

 disarticulating below the spikelet. Glumes well developed in Pharus } 

 a tropical genus placed in this tribe provisionally. 



A small tribe of uncertain affinities, aquatic or subaquatic grasses 

 (except Pharus) of no economic importance except the Indian rice 

 (ZAzania). 



Key to the genera of Zizanieae 



Blades elliptic, 2 to 4 cm wide 117. PHARUS. 



Blades much longer than wide. 



Culms slender; plants low; staminate and pistillate spikelets borne in 



separate inflorescences. 

 Inflorescence a few-flowered raceme; plants not stoloniferous 



116. HYDROCHLOA. 



Inflorescence a panicle; plants stoloniferous 115. LUZIOLA. 



Culms robust; plants tall; staminate and pistillate spikelets borne in the 



same panicle. 



Pistillate spikelets on the ascending upper branches, the staminate on the 

 spreading lower branches of the panicle; plants annual or perennial. 



113. ZIZANIA. 



Pistillate spikelets at the ends, the staminate below on the same branches 

 of the panicle; plants perennial 114. ZIZANIOPSIS. 



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 introduced species, Melinis minutiflora. 



TRIBE 12. PANICEAE' 



Spikelets with one perfect terminal floret and below this a sterile 

 floret and two 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 (Reimar- 

 ochloa). 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 Tricholaena. In Eriochloa and in some 

 species of Brachiaria the fertile lemma is awn- tipped. In Setaria 

 there are, beneath the spikelet, one or more bristles, these representing 

 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 two 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 paricle not perfecting grains, the 

 fruitful spikelets borne on subterranean branches __ 138. AMPHICAEPUM. 



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

 the same panicle. Blades broad, elliptic 139. OLYRA. 



