A new species of the myxomycete genus Perichaena is described in this paper. The new species, named Perichaena calongei, was found during intensive studies of arid areas of the Monte desert in Argentina. It has been found directly in the field from the provinces of Catamarca, La Rioja, Salta and San Juan, in the Northwest of Argentina, and isolated from moist chamber cultures of native plant species collected in Catamarca, Jujuy, Salta and San Juan. The characters that make this species unique in the genus are the combination of the morphology of the sporocarps, the structure and dehiscence of the peridium, and the ornamentation of the capillitium. The morphology of the my xomycete specimens was examined using light microscopy with Nomarski interference contrast, and scanning electron microscopy. Micrographs of relevant morphological characters are included. A key to facilitate the identification of the stipitate species of Perichaena is also proposed. Se describe una nueva especie, Perichaena calongei, que fue encontrada en el desierto de Monte, en las zonas áridas del noroeste de Argentina. Los cuerpos fructíferos se encontraron fructificados en el campo, también se obtuvieron por cultivo en cá-mara húmeda de plantas recolectadas en las provincias de Catamarca, Jujuy, La Rioja, Salta y San Juan. La combinación de caracteres de la morfología del esporocarpo, de la estructura y tipo de dehiscencia del peridio, y de la ornamentación del capilicio, distinguen esta especie del resto de las conocidas en el gé-nero. La morfología de la especie se analizó con un microscopio óptico dotado de contraste interferencial de Nomarski y con un microscopio electrónico de barrido, se incluyen ilustraciones de las estructuras observadas. Se propone una clave dicotómica para la identificación, a nivel mundial, de las especies estipitadas del género Perichaena.

We report the results of a survey for myxomycetes in the Chinese province of Xinjiang, covering the northern part of the Tarim basin and the eastern Tian-Shan mountains. Sampling in the hyperarid Tarim basin focused on monospecific Tugai forests; these are park-like stands of the phreatophyte Populus euphratica. In a transect from the Tarim basin to the mountains, trees vanish outside the basin, but reoccur at ca. 1,400 m elevation as monospecific forests of Picea schrenkiana; the second focal area of the study. From a total of 362 substrate samples (245 from the Tarim basin, 177 from the mountains) we obtained 477 determinable records of myxomycetes, plus a total of 206 field collections, the latter almost exclusively from the spruce forests in the mountains. From the 80 taxa recorded 53 are represented by field collections, and 32 were found in moist chamber cultures; with a very low overlap in species assemblages found in the field and in cultures. Although receiving less than 50 mm annual precipitation, corticolous myxomycetes were common in the Tugai forests, with Physarum pseudonotabile ad. int., Didymium anellus, Echinostelium colliculosum and Protophysarum phloiogenum as the most common species. Compared to the Tarim basin (21 taxa) the mountains were much richer in myxomycetes (75 taxa), although the diversity recovered from cultures was comparable (21 vs. 28 taxa). Most species from the mountains fruited on decaying spruce, often collected under or even inside the logs due to the extremely dry air. Our results suggest first that there is no lower limit of annual precipitation for myxomycetes, as long as at least some days with nightly dew fall allow these organisms to complete their life cycle. Second, the two examples of surprisingly diverse myxomycete assemblages from monospecific forests demonstrate, that species richness of this group is not necessarily connected with plant diversity of the habitat. This survey is the most eastern of a large-scale study of myxomycete diversity throughout Middle and Central Asia.