New Euphorbiaceae from Mexico

This article contained descriptions of five new taxa of Mexican Euphorbiaceae. Euphorbia (subg. Agaloma) nayarensis is endemic to pine-oak woodland in the mountains of central Nayarit. It appears related to E. soobyi but differs by possessing linear to linear-ovate leaves. Croton varelae is also endemic to central Nayarit. A key was provided to distinguish this species, a member of sect. Geiseleria, from the seven other Mexican species of this section. Croton ramillatus var. magniglandulifer occurs in the states of Guerrero and Morelos. This new variety differs from var. ramillatus by the possession of larger petiolar glands. Croton michaelii occurs in Aguascalientes and Durango. It is uncertain to which section of Croton this species belongs. It resembles Croton yecorensis but is distinguished by possessing a lepidote indumentum and by lacking conspicuous stipitate glands. Croton disjunctus has been collected in Chihuahua and Aguascalientes, at localities separated by more than 600 km. This species appears to be most closely akin to Croton fruticulosus Torr., from which it is separated by glabrous, evident (vs. pubescent, nearly obsolete) stipules and multifid (vs. bifid) styles

Perturbative Quantum Field Theory at Positive Temperatures: An Axiomatic Approach

It is shown that the perturbative expansions of the correlation functions of a relativistic quantum field theory at finite temperature are uniquely determined by the equations of motion and standard axiomatic requirements, including the KMS condition. An explicit expression as a sum over generalized Feynman graphs is derived. The canonical formalism is not used, and the derivation proceeds from the beginning in the thermodynamic limit. No doubling of fields is invoked. An unsolved problem concerning existence of these perturbative expressions is pointed out.Comment: 17pages Late

Euphorbia (Subgen. Chamaesyce Sect. Anisophyllum) jaegeri, a Shrubby New Species from the Deserts of California, United States

Euphorbia jaegeri (Euphorbiaceae), an endemic to southeastern California, United States, is described as new and illustrated with photographs. It is known from two general locations, one in the Orocopia Mountains (Riverside County) and the other in the Marble Mountains and adjacent Bristol Mountains (San Bernardino County). The habitat is desert scrub on rocky hillsides and along arroyos, primarily in rock crevices or gravelly soils, at elevations from approximately 600 to 850 m. The new species belongs to Euphorbia subgen. Chamaesyce sect. Anisophyllum. It is distinguished by the combination of a shrubby habit and involucral appendages that are deeply parted into triangular to subulate segments. The exact affinities of the new species are not obvious, but it is compared with E. polycarpa and E. setiloba. With only four known occurrences, a fragmented distribution, and significant existing and potential threats to most of the populations, E. jaegeri is of high conservation concern

The Euphorbiaceae of Sonora, Mexico

This publication is an account of the Euphorbiaceae in the state of Sonora, México. Nineteen genera, 143 species, and three additional varieties are recorded for the state; three species expected within the state are also treated. One species of Acalypha and three species and one subspecies of Euphorbia are described. Dichotomous keys for the identification of genera and species are provided. Bibliographic citations, type information, synonyms, brief habit descriptions, times of reproduction, habitat preferences as well as elevational range within Sonora, geographical distribution, and representative specimens are given for each species. When appropriate, notes on uses, taxonomic or nomenclatural problems, and other points of interest are discussed

Assessing the Potential of Sulfur Isotopes and Trace Metals as Chemostratigraphic Correlation Tools in the “Mississippian Limestone” of the Midcontinent

The “Mississippian Limestone” in the Midcontinent, United States, has proven to be a prolific hydrocarbon reservoir and has been intensely studied with regard to lithology, sequence stratigraphy, and facies distribution. Discontinuous lithology and heterogeneous facies of complex carbonate systems, however, make conventional correlation methods, such as lithostratigraphy, difficult. Two novel chemostratigraphic tools may provide a solution to this correlation-challenge: the sulfur isotope composition of carbonate associated sulfate (CAS), which is used as a proxy for the isotope composition of seawater sulfate at the time of carbonate formation and has been successfully applied to reconstruct changes in biogeochemical sulfur cycling on a global scale, and trace metals (TMs), which have been successfully applied in shales as proxies for paleoseawater redox conditions. Utilizing a framework of sequence stratigraphy for the Mississippian limestone in southwest Missouri, we tested the application of CAS isotopes and TM content as correlation tools on samples taken along vertical and horizontal transects from the St. Joe Group. The sulfur concentration and isotope composition of CAS were determined using a leaching and dissolution procedure. The TM content was determined for the carbonate fraction as well as the bulk rock fraction including the siliciclastic phases; samples were analyzed by inductively coupled plasma mass spectrometry. CAS results show a good correlation of the sulfur isotope signal along a lateral transect over hundreds of meters and reflect temporal variations on time scales similar to 3rd-order sequence cycles. The sulfur isotope composition also indicates that the basin was open to global seawater circulation during deposition. Although potential for high-resolution characterization is limited in open ocean basins, CAS isotopes may prove more effective when used for correlation in restricted basin settings. The TM results suggest fluctuating Cd, P, and Ti content on 3rd-order and higher time-scales. The lack of V, U, and Mo enrichments indicate that the rocks were deposited in an oxic environment. Although the effectiveness of CAS and TMs as correlation tools may be limited by the sampling resolution in our study, both parameters can be used to reconstruct the oceanographic conditions of the basin during deposition and thus provide useful information.Geolog

Meliosma mexicana (Sabiaceae), una especie nueva de la Sierra Madre Oriental de México

Meliosma mexicana (Sabiaceae) is described as a new species. It occurs in the Sierra Madre Oriental of Mexico in the states of Querétaro and Tamaulipas, growing primarily in cloud forest and humid pine-oak forest at elevations of 800 to 1900 m. It belongs to subg. Meliosma sect. Lorenzanea. It is most similar to M. dentata, which it apparently replaces in northeastern Mexico. Meliosma mexicana is distinguished from M. dentata in having essentially entire leaves, stipitate glandular trichomes that vary from red to blackish, and subglobose fruits 0.6 to 0.7(0.8) cm long.Se describe como especie nueva a Meliosma mexicana (Sabiaceae). Es endémica de la Sierra Madre Oriental de México en los estados de Querétaro y Tamaulipas. Crece desde los 800 hasta los 1900 m de altitud en el bosque mesófilo de montaña y el bosque de pino-encino húmedo. Pertenece al subg. Meliosma sect. Lorenzanea y es morfológicamente parecida a M. dentata, a la cual aparentemente remplaza en el noreste de México. Meliosma mexicana se distingue de M. dentata por tener hojas esencialmente enteras, glándulas estipitadas que varían de color rojizo a negruzco, y frutos subglobosos de 0.6 a 0.7(0.8) cm de largo

MELIOSMA MEXICANA (SABIACEAE), UNA ESPECIE NUEVA DE LA SIERRA MADRE ORIENTAL DE MÉXICO

Meliosma mexicana (Sabiaceae) is described as a new species. It occurs in the Sierra Madre Oriental of Mexico in the states of Querétaro and Tamaulipas, growing primarily in cloud forest and humid pine-oak forest at elevations of 800 to 1900 m. It belongs to subg. Meliosma sect. Lorenzanea. It is most similar to M. dentata, which it apparently replaces in northeastern Mexico. Meliosma mexicana is distinguished from M. dentata in having essentially entire leaves, stipitate glandular trichomes that vary from red to blackish, and subglobose fruits 0.6 to 0.7(0.8) cm long.Se describe como especie nueva a Meliosma mexicana (Sabiaceae). Es endémica de la Sierra Madre Oriental de México en los estados de Querétaro y Tamaulipas. Crece desde los 800 hasta los 1900 m de altitud en el bosque mesófilo de montaña y el bosque de pino-encino húmedo. Pertenece al subg. Meliosma sect. Lorenzanea y es morfológicamente parecida a M. dentata, a la cual aparentemente remplaza en el noreste de México. Meliosma mexicana se distingue de M. dentata por tener hojas esencialmente enteras, glándulas estipitadas que varían de color rojizo a negruzco, y frutos subglobosos de 0.6 a 0.7(0.8) cm de largo