Plants annual or perennial; habit various. Culms 3-800 cm, annual, usually not woody. Leaves basal and/or cauline; sheaths usually open; ligules of hairs or membranous, membranous ligules often ciliate, cilia sometimes longer than the membranous base; blades occasionally pseudopetiolate, seldom disarticulating at maturity. Inflorescences terminal, sometimes also axillary, occasionally subterranean panicles; branches sometimes spikelike and secund, sometimes less than 1 cm; disarticulation usually below the glumes, sometimes at the base of the panicle branches, occasionally below the florets. Spikelets usually dorsally compressed, varying to terete or laterally compressed, with 2(3) florets, lower florets staminate, sterile, or reduced, upper florets usually bisexual; calluses not developed. Glumes usually membranous; lower glumes usually less than 1/2 as long as the spikelets, sometimes absent; upper glumes usually subequal to the upper florets, occasionally absent; lower lemmas similar to the upper glumes in length and texture; upper lemmas indurate, coriaceous, or cartilaginous, with a germination flap at the base, margins usually widely separated and involute at maturity, sometimes flat and hyaline; upper paleas similar to the upper lemmas in length and texture; lodicules short; anthers usually 3; stigmasusually red. Caryopses usually dorsally compressed or terete; embryos 1/2 or more the length of the caryopses. x = 9, 10.

The tribe Paniceae, which includes about 100 genera and 2000 species, is primarily tropical in distribution. Within the Flora region, it is represented by 27 genera and 262 species, with its greatest representation being in the eastern portion of the contiguous United States (Barkworth and Capels 2000).

The tribe is so morphologically distinct that it was first recognized, in essentially its current sense, by Robert Brown in 1814. Its primary distinguishing features are the unusual spikelet structure combined with the indurate to coriaceous upper florets. Recent molecular studies (Barber et al. 2002; Giussani et al. 2001) show it as comprising two distinct lineages, one of which contains species with a base number of x = 9 and the other, species with x = 10.

Photosynthesis in the Paniceae may follow the C₃ pathway or any of three different C₄ pathways. Most genera are uniform in this regard, but there are some noteworthy exceptions. Giussani et al. (2001) concluded that the C₃ pathway is probably ancestral within the tribe and that two of the three C₄pathways, NAD-ME and PCK, originated only once within the tribe, whereas the NADP-ME pathway originated independently in several different lineages. Most genera are uniform with respect to their photosynthetic pathway, but there are some noteworthy exceptions.

The germination flap is a small area of soft tissue at the base of the upper lemma through which the primary root of the seedling grows.

SELECTED REFERENCES Barber, J.C., S.A. Aliscioni, L.M. Giussani, J.D. Noll, M.R. Duvall, and E.A. Kellogg. 2002. Combined analyses of three independent datasets to investigate phylogeny of Poaceae subfamily Panicoideae. Combined analyses of three independent datasets to investigate phylogeny of Poaceae subfamily Panicoideae. [Abstract.] http://www.botany2002.org/; Barkworth, M.E. and K.M. Capels. 2000. The Poaceae in North America: A geographic perspective. Pp. 327-346 in S.W.L. Jacobs and J. Everett (eds.). Grasses: Systematics and Evolution. International Symposium on Grass Systematics and Evolution (3rd:1998). CSIRO Publishing, Collingwood, Victoria, Australia. 408 pp.; Brown, R. 1814. General remarks, geographical and systematical, on the botany of Terra Australis. Pp. 533-613 in M. Flinders (ed.). A Voyage to Terra Australis, vol. 2. G. and W. Nicol, London, England. 613 pp.; Doust, A.N. and E.A. Kellogg. 2002. Inflorescence diversification in the panicoid Bristle Grass clade (Paniceae, Poaceae): Evidence from molecular phylogenies and developmental morphology. Amer. J. Bot. 89:1203-1222; Giussani, L.M., J.H. Cota-Sánchez, F.O. Zuloaga, and E.A. Kellogg. 2001. A molecular phylogeny of the grass subfamily Panicoideae (Poaceae) shows multiple origins of C₄ photosynthesis. Amer. J. Bot. 88:1993-2001; Gómez-Martínez, R. and A. Culham. 2000. Phylogeny of the subfamily Panicoideae with emphasis on the tribe Paniceae: Evidence from the trnL-F cpDNA region. Pp. 136-140 in S.W.L. Jacobs and J. Everett (eds.). Grasses: Systematics and Evolution. International Symposium on Grass Systematics and Evolution (3rd:1998). CSIRO Publishing, Collingwood, Victoria, Australia. 408 pp.