Plants annual or perennial. Culms 1-500 cm, not woody, usually not branched above the base. Sheaths usually open, often with coarse hairs at the top; auricles rarely present; ligules of hairs or membranous, if membranous, often ciliate, cilia sometimes longer than the membranous base; bladesoften with stiff, coarse marginal hairs adjacent to the ligules, glabrous or variously pubescent elsewhere. Inflorescences terminal, sometimes also axillary, simple panicles, panicles of 1-many spikelike branches, spikelike racemes, spikes, or, in 1 genus, a solitary spikelet, in dioecious taxa the staminate and pistillate inflorescences sometimes morphologically distinct; disarticulation usually beneath the fertile florets or the glumes but, particularly if the panicle branches are short, sometimes at the base of the branches. Spikelets usually laterally compressed, with 1-60 florets, sterile or reduced florets, if present, usually distal to the bisexual florets. Glumes from shorter than the adjacent florets to exceeding the distal florets; lemmas 1-3-veined or 7-13-veined, rarely 5-veined, if with 7-13 veins, the veins often in 3 groups; lodicules 2, or absent. x = 7, 8, 9, 10, 12.

Most members of the Cynodonteae in the Flora region can be recognized by their possession of two or more of the following characteristics: 1-3- or 7-13-veined lemmas, laterally compressed spikelets, spikelike inflorescence branches, and the presence of coarse hairs near the junction of the sheath and blade. All employ the NAD-ME or PCK C₄ photosynthetic pathways, have Kranz blade anatomy, and tend to grow in hot, dry areas. Having said this, it must be acknowledged that each of these characteristics can be found in other tribes and, within the Cynodonteae, there are genera that lack one or more of them. Nevertheless, it is usually fairly easy to recognize members of the tribe.

The tribe Cynodonteae, as interpreted here, includes genera that are normally placed in two tribes, the Cynodonteae sensu stricto and the Eragrostideae Stapf (Clayton and Renvoize 1986; Peterson et al. 2001; Grass Phylogeny Working Group 2001, but see Campbell 1985). Genera 17.01 to 17.34 correspond to the Eragrostideae of Clayton and Renvoize, and genera 17.35 to 17.53 to the Cynodonteae. The two are treated as one here because recent morphological, anatomical, and molecular studies (Van den Borre 1994; Van den Borre and Watson 1997; Hilu and Alice 2001) indicate that the distinction between the two is artificial, but there is no agreement on an alternative treatment. Part of the problem is that several of the genera (e.g., Eragrostis, Chloris, Muhlenbergia, and Sporobolus) are polythetic (Van den Borre and Watson 1997; Hilu and Alice 2001). The uncertainty concerning relationships within the tribe is reflected in the classification of Peterson et al. (2001), which lists 23 of the 53 genera treated here as being of uncertain position within the subfamily Chloridoideae.

SELECTED REFERENCES Campbell, C.S. 1985. The subfamilies and tribes of Gramineae (Poaceae) in the southeastern United States. J. Arnold Arbor. 66:123-199; Clark, L.G., W. Zhang, and J.F. Wendel. 1995. A phylogeny of the grass family (Poaceae) based on ndhF sequence data. Syst. Bot. 20:436-460; Clayton, W.D. and S.A. Renvoize. 1986. Genera Graminum: Grasses of the World. Kew Bull., Addit. Ser. 13. Her Majesty's Stationery Office, London, England. 389 pp.; Columbus, J.T., M.S. Kinney, R. Pant and M.E. Siqueiros Delgado. 1998. Cladistic parsimony analysis of internal transcribed spacer region (nrDNA) sequences of Boutelouaand relatives (Gramineae: Chloridoideae). Aliso 17:99-130; Grass Phylogeny Working Group. 2001. Phylogeny and subfamilial classification of the grasses (Poaceae). Ann. Missouri Bot. Gard. 88:373-457; Hilu, K.W. and L.A. Alice. 2001. A phylogeny of the Chloridoideae (Poaceae) based on matK sequences. Syst. Bot. 26:386-405; Peterson, P.M., R.J. Soreng, G. Davidse, T.S. Filgueras, F.O. Zuloaga, and E. Judziewicz. 2001. Catalogue of New World Grasses (Poaceae): II. Subfamily Chloridoideae. Contr. U.S. Natl. Herb. 41:1-255; Peterson, P.M., R.D. Webster, and J. Valdés-Reyna. 1995. Subtribal classification of the New World Eragrostideae (Poaceae: Chloridoideae). Sida 16:529-544; Van den Borre, A. 1994. A taxonomy of the Chloridoideae (Poaceae), with special reference to the genus Eragrostis. Ph.D. dissertation, Australian National University, Canberra, New South Wales, Australia. 313 pp.; Van den Borre, A. and L. Watson. 1997. On the classification of the Chloridoideae (Poaceae). Austral. Syst. Bot. 10:491-531.