Resumen. Se evaluó la variación espacial de la es tructura de la sinusia arbórea (d.a.p. ;::: 3.18 CITl; perímetro ;::: 10 c/Tl) del bosque mesófilo d e monta1ia (BMM) en Puerto Soledad, Oaxaca, mu est rea ndo con la técnica de cuadrantes centrados en seis unidades topográficas contrastantes (laderas este, oeste, norte y sur, cima y cañada húm eda) . La densidad fluctuó entre 505 y 2,730 ind ha·' y e l área basal entre 41.8 y 172 m' ha·'. La estructura en la cima fue muy diferente de la descrita en otros amb ientes, ya que allí se obtuvo la me nor densidad y la mayor área basal. La cobertura total del bosque fue> 150 % en todos los ambientes. La altura del dosel varió entre 20 )' 35 m, y e n nin gú n sitio se presentó una estratificación bien definida. Las especies estructuralm e nte importa ntes fueron Arctostaphylos a.1guta, Clethra. lica.noides, C. mexicana, Cya.th.ea. fulva., Ilex discolo· 1; Podoca1jJus ieichei, Quercus acherdophylla., Q. eu.genifolia., Q. 1ysojJhylla. y Ternstmemia linea.ta. Las estructuras diamétricas de las poblaciones más abundantes fueron mu y variables, pero en general las clases de diámetros más pequeños fu eron las mejor representadas. Alrededor del 12% de las 34 parejas de especies examinadas en los sitios de muestreo mostraron asociaciones significativas y negativas. Aunque en general los valores estructurales del BMM de Puerto Soledad caen dentro de los intervalos conocidos para otros bosqu es similares, los resultados indi can clara me nte que la vegetación de Puerto Soledad es muy heterogénea, si bien esta variabilidad es más notable para a lgunos atributos estructurales (e.g. densidad, área basal) que para otros (e.g. cobertura). El estudio refuerza la idea de que bajo el concepto de BMM se agrupa un conjunto heterogéneo de com unidades vegetales. Palabras clave: bosque mesófilo de monta1ia, estructura del bosque, es tructuras poblacionales, heteroge neidad es pacia l, montañas tropicales, Oaxaca. Abstract. Spatial variation of a mesop h yll ous montane forest (=cloud forest, montane rain forest) tree community structure (dbh;::: 3.18 cm; g irth;::: 10 cm) was evaluated by sampling with the point-centered quadrat technique at six contrasting e nvironme nts at Puerto Soledad, Oaxaca: East-facing slope, North-facing slope, West-facing slope, South-facing slope, Mountain Top and v\'et Ravine. Density ranged between 505 and 2,730 ind ha·', and basal area between 41.8 and 172 rn' ha·'. Forest structure at the Mountain Top greatly differed from that in other environments, as the smallest density and largest basal area were found there. Total canopy cover was > 150% in ali environments. Canopy height ranged between 20 and 35 m; no well defined strata were found at any site. Structurally important species were: Arctosta.phylos mguta, Clethm. licanoides, C. mexicana, Cyathea Julva, Ilex discolor, Podocmjms reichei, Quercus acherdophylla, Q. eu.genifolia, Q. 1)'sophylla. and Ternstroernia lineata. Diameter-based population structures for the most abundant spec ies were very variable, bu...

A new legume species from a seasonally dry forest of the Western Río Balsas Depression, in the states of Guerrero and Michoacán, Mexico, Erythrostemon guevarafeferii, is herein described and illustrated. The new species shows morphological affinities with Erythrostemon hintonii, from which it is distinguished in having fewer leaflets per pinna, mature leaflets disposed toward the upper half of the pinnae rachises, long inflorescences on curved slender peduncles, abundant red glands on its flowers and inflorescences, and its fruit glabrous with red stipitate glands at maturity. A taxonomic key to the Río Balsas Depression species of Erythrostemon is included.

Abstract— A new species of the genus Coulteria from the seasonally dry forest of the Rio Balsas Depression, Mexico is described and illustrated. Coulteria sousae is morphologically most similar to Coulteria pringlei but differs from it by having smaller flowers (1 cm long), long stipitate fruit, leaflets that are glabrous and coriaceous at maturity, and an allopatric distribution. The conservation status of this species is suggested to be Endangered (EN), according to the IUCN Red List Categories and Criteria.

A new legume species, Erythrostemon sousanus, from seasonally dry forest of the Río Papagayo Basin in Guerrero, Mexico is described and illustrated. The new species is morphologically similar to E. mexicanus, from which it is distinguished by its glabrous leaves with a greater number of pairs of pinnae (6-11 vs 5-7) and each pinna with more pairs of leaflets (5-7 vs 2-4); by flowers, inflorescences and fruits densely pubescent; and by larger flowers (13-17 vs 12 mm long), fruits (8 × 2 vs 4 × 1.5 cm) and seeds (12 × 9 × 2 vs 9-10 × 7.5 ×1.5 mm).

Distichlis spicata var. stricta (L) Greene is a grass able to grow during drought or flooding seasons, as well as in poor, saline, and alkaline soils, making it an ideal model system to study salinity and water stress tolerance in plants. However, it is known to have an extremely low germination rate in the field, as low as 3%. Here, we established in vitro conditions to study the factors that affect D. spicata under osmotic and salt stress. Treatments that included mechanical scarification, 4°C stratification, and 20% NaDCC (w/v) disinfection significantly increased the germination rate up to 84% in only 5 days. Furthermore, saltgrass had good seed germination under high salinity (ionic) stress caused by 150 and 200 mM NaCl (50% and 30%, respectively). Saltgrass was sensitive to osmotic agents Mannitol and Sorbitol during the germination stage, suggesting that this is a main limiting developmental stage for D. spicata success under osmotic environments.