Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Elaeagia Wedd., a genus of some 16 species belonging to the tribe Rondeletieae, is centered in South America with a single species known from Cuba. Two additional species occur in Central America, one of which, E. nitidifolia Dwyer, is known only from Panama. The other, E. auriculata Hemsl., extends as far north as Guatemala (Standley & Williams , 1975; Dwyer, 1980). Most members are large trees, some attaining 35 meters, although the Cuban species is said to be shrubby (Standley, 1921). All known species occur in montane forest at altitudes of 800 to 2 800 meters. Consequently, it was surprising to see material, apparently representing an undescribed species, from lowland tropical rain forest in SE Oaxaca and adjacent Veracruz in Mexico. However, Dr. Tom Wendt's collecting efforts towards a woody flora of the Uxpanapa Zone have yielded a number of range extensions for taxa previously known only from Central America or Chiapas. Significantly, this region lies at the northern limits of the area to be included in Flora Mesoamericana. An additional collection is known from montane forest at 1 100 m in northern Chiapas, a habitat more typical for the genus .

The arboreal vegetation of a portion of the Tehuacán-Cuicatlán Valley is analyzed. An altitudinal gradient was followed along the leeward slopes of the Sierras de Juarez and Zongolica (Sierra Madre Oriental). Multivariate analysis techniques, ordination (principal component analysis and reciprocal averaging) and classification (informationanalysis program CENOSIS 2) were used. The results allow the definition of "groups" identifiable with vegetation types defined from a physiognomic-structural view point; however, the analysis performed shows that the arboreal vegetation of the study area possesses a variability and heterogeneity not detected by previous descriptive physiognomic studies. The importance of human disturbance and other factors (e.g. biotic interactions) affecting the structure and composition of the plant communities of the study area is discussed . The analysis techniques are compared with regards to their efficiency in handling high levels of vegetational heterogeneity , being the classification technique the most efficient one. Finally, some considerations judged interesting for future investigations are proposed.

Book Review

Book review

The Cyperaceae are widely distributed in the Valley of Mexico, practically in all vegetation types, but mainly in wet or inundated soil within oak forests, grasslands, pine forests, xerophilous scrubs and pine forests, in an altitudinal range of 2 230 to 4 100 m. Several are evident aquatics, like all the species of Scirpus, some of Eleocharis as well as a few of Cyperus and Carex, but there are also other adapted to conditions of reduced humidity. The reproductive phenology of most of the species is linked with the rain y season; only some of the evident aquatics can be found in flower almost the year round.

Some taxonomical problems related with Gnaphalium americanum Mill.; C. conoideum H.B.K.; C. liebmanii Sch. Bip. ex Klatt; C. oxyphyllum DC. and G. inornatum DC. are discussed. G. oxyphyllum var. nataliae is described as a new variety; G. panniforme. Blake is reduced to G. nubicola var. panniforme and Chionolaena sartorii Klatt is transfered to Gnaphalium sartorii.

Vestured pits and different kinds of inclusions was searched for under the scanning microscope in five species of Cordia and one of Bourreria. Calcium oxalate crystals and tyloses were found in all five species of Cordia while in B. purpusii crystals were found but not tyloses . Vestured pits were found in C. alliodora , C. elaeagnoides and B. purpussi, starch was also found in the fibres and parenchyma of C. alliodora and C. dentata.

-

-

Crassulaceae acid metabolism (CAM) is frequent in many plants in arid zones but can also be found in very humid environments, mainly in epiphytic and hemiepiphytic plants.