CALAMAGROSTIS COAHUILENSIS AND C. DIVARICATA (POACEAE: POOIDEAE: AGROSTIDINAE), TWO NEW SPECIES FROM MEXICO Paul M. Peterson and Robert J. Soreng Jesus Valdes-Reyna Department of Botany Departamento de Botanica National Museum of Natural History Univerisidad Autonoma Agraria "Antonio Narro" Smithsonian Institution Buenavista,Saltillo Washington, District of Columbia 20013-7012, U.S.A. Coahuila 25315, MEXICO peterson.paul@nmnh.si.edu; soreng.rob@nmnh.si.edu jvaldes@narro.uaaan.mx ABSTRACT Calamagrostis coahuilensis P.M. Peterson, Soreng & Valdes-Reyna, sp. nov., and Calamagrostis divaricata P. M. Peterson & Soreng, sp. nov, from Mexico are described and illustrated. Calamagrostis coahuilensis occurs on calcareous slopes in the mountains of southeastern Coahuila and southwestern Nuevo Leon; and C. divaricata occurs on moist slopes and mossy cliffs of southwestern Durango. Calamagrostis coahuilensisis morphologically similar to C. purpurascens but differs by having shorter anthers (1-1.2 mm long), nearly smooth ligules, scaberulous rachises, glabrous or minutely antrorsely scabrous sheath summits, and somewhat dense but not spikelike, greenish panicles. Calamagrostis divaricata seems morphologically allied to C. pringlei but differs by having wider panicles (4-10 cm) with branches reflexed spreading and divaricate, shorter spikelets (3.4-4.3 mm long), shorter glumes (3.4-4.3 mm long) that are both 1-veined, and shorter lemmas (3.8-4.3 mm long) with an awn inserted on upper 1/4 to 1/3. RESUMEN Se describen y se ilustran para Mexico Calamagrostis coahuilensis P.M. Peterson, Soreng & Valdes- Reyna, sp. nov, y Calamagrostis divaricata P.M. Peterson & Soreng, sp. nov. Calamagrostis coahuilensis se encuentra en laderas calcareas en las montanas del sureste del estado de Coahuila y suroeste del estado Nuevo Leon; y C divaricata se encuentra en laderas humedas y riscos musgosos del suroeste del estado de Durango. Calamagrostis coahuilensis es morfologicamente similar a C. purpurascens pero difiere en poseer anteras mas cortas (1-1.2 mm largo), ligulas casi lisas, raquis escaberuloso, apices de las vainas glabros o escasamente con escabrosidad antrosa, y paniculas densas pero no espigadas. de color verdusco. Calamagrostis divaricata parece morfologicamente relacionado a C. pringlei pero difiere en poseer paniculas mas amplias (4-10 cm) con ramificaciones reflexas, extendidas y divaricadas, espiguillas mas cortas (3.4-4.3 mm largo), glumas mas cortas (3.4-4.3 mm largo) ambas uninervadas, y lemas mas cortas (3.8-4.3 mm largo) con una arista insertada desde 1/4 hasta 1/3 arriba de la mitad. Calamagrostis is characterized as having single-flowered spikelets, one or three- veined glumes as long or exceeding the floret in length (rarely slightly shorter), non-keeled lemmas that are membranous or cartilaginous (infrequently hya- line), usually with a single dorsally attached awn (rarely awnless), a callus with a crown of hairs, caryopses with short hilums and without apical hairs, and lodicules that are apically membranous (Clayton & Renvoize 1986; Watson & SIDA21(1):311 -320.2004