Paul M. Peterson

Plants annual or perennial; usually synoecious, sometimes dioecious; cespitose, stoloniferous, or rhizomatous. Culms 2-160 cm, not woody, erect, decumbent, or geniculate, sometimes rooting at the lower nodes, simple or branched; internodes solid or hollow. Leaves not strongly distichous; sheaths open, often with tufts of hairs at the apices, hairs 0.3-8 mm; ligules usually membranous and ciliolate or ciliate, cilia sometimes longer than the membranous base, occasionally of hairs or membranous and non-ciliate; blades flat, folded, or involute. Inflorescences terminal, sometimes also axillary, simple panicles, open to contracted or spikelike, terminal panicles usually exceeding the upper leaves; pulvini in the axils of the primary branches glabrous or not; branches not spikelike, not disarticulating. Spikelets 1-27 mm long, 0.5-9 mm wide, laterally compressed, with (1)2-60 florets; disarticulation below the fertile florets, sometimes also below the glumes, acropetal with deciduous glumes and lemmas but persistent paleas, or basipetal with the glumes often persistent and the florets usually falling intact. Glumes usually shorter than the adjacent lemmas, 1(3)-veined, not lobed, apices obtuse to acute, unawned; calluses glabrous or sparsely pubescent; lemmas usually glabrous, obtuse to acute, (1)3(5)-veined, usually keeled, unawned or mucronate; paleas shorter than the lemmas, longitudinally bowed-out by the caryopses, 2-keeled, keels usually ciliate, intercostal region membranous or hyaline; anthers 2-3; ovaries glabrous; styles free to the bases. Cleistogamous spikelets occasionally present, sometimes on the axillary panicles, sometimes on the terminal panicles. Caryopses variously shaped. x = 10. The origin of the name is obscure.

Eragrostis, a genus of approximately 350 species, grows in tropical and subtropical regions throughout the world. About 110 species are native or adventive in the Western Hemisphere; 25 species are native in the Flora region, 24 are introduced. In most taxa native to the Western Hemisphere, disarticulation is acropetal and the lemmas fall with the caryopses, leaving the paleas attached to the rachilla.

Van den Borre and Watson (2000) and Hilu and Alice (2001) suggested that Eragrostis might not be monophyletic. Ingram and Doyle (2004), based on nuclear and plastid sequence data, conclued that it is, if four segregate genera are included: Acamptocladus, Diandrochloa, Neeragrostis, and Pogonarthria. We are not, at this stage, prepared to emend the treatments of Eragrostis and Pogonarthria to reflect these findings. [Note added by Barkworth, 2004.]

Nathaniel Wolf (1776), the person who first named Eragrostis, made no statement concerning the origin of its name. Clifford (1996) provides three possible derivations: from eros, love, and Agrostis, the Greek name for an indeterminate herb; from the Greek er, early and agrostis, wild, referring to the fact that some species of Eragrostis are early invaders of arable land; or the Greek eri-, a prefix meaning very or much, suggesting that the name means many-flowered Agrostis. Many authors have stated that the first portion of the name is derived from eros, but none have explained the connection between Eragrostis and passionate expressions of love, the kind of love to which eros applies.

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SELECTED REFERENCES Clifford, H.T. 1996. Etymological Dictionary of Grasses, Version 1.0 (CD-ROM). Expert Center for Taxonomic Identification, Amsterdam, The Netherlands; Harvey, L.H. 1948. Eragrostis in North and Middle America. Ph.D. dissertation, University of Michigan, Ann Arbor, Michigan, U.S.A. 269 pp.; Harvey, L.H. 1975. Eragrostis. Pp. 177-201 in F.W. Gould. The Grasses ofTexas. Texas A&M University Press, College Station, Texas, U.S.A. 635 pp.; Hilu, K.W. and L.A. Alice. 2001. A phylogeny of Chloridoideae (Poaceae) based on matK sequences. Syst. Bot. 26:386-405; Ingram, A.A. and J.J. Doyle. 2004. Is Eragrostis (Poaceae) monophyletic? Insights from nuclear and plastid sequence data. Syst. Bot. 29:545-552; Koch, S.D. 1974. The Eragrostis pectinacea- pilosa complex in North and Central America. Illinois Biol. Monogr. 48:1-74; Sánchez Vega, I. and S.D. Koch. 1988. Estudio biosistemático de Eragrostis mexicana, E. neomexicana, E. orcuttiana, y E. virescens (Gramineae: Chloridoideae). Bol. Soc. Bot. 48:95-112; Van den Borre, A. and L. Watson. 2000. On the classification of the Chloridoideae: Results from morphological and leaf anatomical data analyses. Pp. 180-183 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.; Wolf, N.M. 1776. Genera Plantarum. [publisher unknown, Danzig, Germany]. 177 pp.

T.A. Cope (1993) Poaceae Flora of Somalia 4: 148-270

Plants annual or perennial. Leaves: ligules usually a line of hairs, rarely a membrane. Inflorescences usually open or contracted panicles, rarely of spikelike branches on an elongated axis. Spikelets with 2-many florets, orbicular to lanceolate; disarticulation varied. Glumes often deciduous, usually 1-, rarely 3-veined; lemmas 3-veined, keeled or rounded on the back, membranous to coriaceous, usually glabrous to scabridulous, rarely hairy, entire, truncate to acuminate, sometimes mucronate; palea keels sometimes winged or siliate; anthers 2-3. Fruits usually globose to ellipsoid, usually a caryopsis but sometimes the pericarp free.

Eragrostis includes about 350 species which grow primarily in the tropics and subtropics. There were 24 species known from Somaliland and Somalia when the Flora of Somalia was published. 

Key to the species of Eragrostis in Somaliland and Somalia.

Global distribution of Eragrostis.