Se describe e ilustra a <span class="font5">Arbutus bicolor </span><span class="font1">S. González, M. González et P. D. Sørensen, sp. nov., especie relacionada con </span><span class="font5">A. xalapensis </span><span class="font1">H.B.K., que ha sido por largo tiempo identificada erróneamente como </span><span class="font5">A. glandulosa </span><span class="font1">M. Martens & Galeotti, un sinónimo de esta última. Se diferencia de </span><span class="font5">A. xalapensis </span><span class="font1">por tener las ramillas y pecíolos densamente glandular pubescentes, las hojas marcadamente bicolores con envés blanquecino a ocre pálido debido a la presencia de indumento denso y uniforme de pelos apretadamente crespos, las hojas de color rojo intenso en la senescencia, así como las flores de color rosa o raramente blanco. Arbutus bicolor está ampliamente distribuida en la Sierra Madre Occidental y el Eje Neovolcánico, alcanzando la vertiente occidental de la Sierra Madre Oriental. Se registran híbridos esporádicos con A. madrensis S. González, A. occidentalis McVaugh & Rosatti, A. tessellata Sørensen y A. xalapensis. Se incluye una clave para distinguir a A. bicolor de otras especies arbóreas de Arbutus de México.
Dahlia campanulata and D. cuspidata (Asteraceae, Coreopsideae), two new species from the Mexican states of Oaxaca and Hidalgo, respectively, are described and illustrated. Dahlia campanulata is distinguished by its exceptionally large, pendulous, and campanulate flower heads; leaf petioles with enlarged clasping bases that are much thicker than in any other species of Dahlia; and enormous tubers that exceed 0.5 m in length. Dahlia cuspidata is distinguished by its large outer involucral bracts and cuspidate leaflets, particularly at the terminal end of the rachis and those at the ends of the lateral rachillae; the terminal leaflet on mature leaves is often much more rounded (versus elliptic) than the lateral leaflets.Key words: Asteraceae, Coreopsideae, Dahlia, Heliantheae sensu lato, Hidalgo, Mexico, Oaxaca.
RESUMENSe describen e ilustran Dahlia campanulata y D. cuspidata (Asteraceae, Coreopsideae), dos nuevas especies de los estados mexicanos de Oaxaca e Hidalgo respectivamente. Dahlia campanulata se distingue porque las cabezuelas de las flores son excepcionalmente grandes, campanuladas y péndulas, las bases de los pecíolos son alargadas y amplexicaules, mucho más gruesas que en cualquier otra especie; los tubérculos son enormes y exceden 0.5 m de largo. Dahlia cuspidata se distingue por sus brácteas involucrales externas grandes y sus folíolos cuspidados, especialmente el que remata el 1 Current address:
Dahlia parvibracteata (Asteraceae, Coreopsideae), a new species from Guerrero, Mex¬ ico, is described and illustrated. It is distinguished by its numerous flowers on terminal or axillary stems, either borne singly on long peduncles or on short-branching naked stems held above the fo¬ liage, and by its narrowly spatulate to oblong-lan¬ ceolate outer involucral bracts. This species falls within the natural range for the genus, and is mor¬ phologically closest to D. moorei, although there are distinct differences.
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