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Asplenium (Aspleniaceae) is taxonomically one of the most complex fern genera with about 700 species, nearly cosmopolitan in distribution. In Argentina, Asplenium constitutes the most speciesrich fern genus, with 38 taxa. Among these species, the delimitation of Asplenium achalense remain poorly understood. Some authors consider A. serra as a variant of A. achalense, or even the last species has been considered as a complex of species. The finding of a population of Asplenium achalense in Yungas after three decades without observations in the wild and neither registering more recently herbarium specimens, made it possible to analyse living material and observe new diagnostic characters present in rachises and laminae scales, glandular hairs in petioles and rachises along with spore wall features, that are critical to delimitate A. achalense as a well-defined taxon, endemics of north-west to central Argentina. [ABSTRACT FROM AUTHOR]

Background and aims: The morphology and the anatomy of the petioles provide useful information for taxonomic issues in ferns. The aim of this study was to analyze the diagnostic characters of petioles in 37 species of Asplenium that grow in Argentina, to contribute to their identification and to ascertain on their adaptive significance. M&M: Herbarium specimens and fresh material were employed. Materials were analyzed under stereoscopic and light microscopes; in the latter case, the samples were processed following the conventional histological techniques. The characters analyzed were: colour, length, presence of wings, sub-epidermic mechanical tissue, aeration lines, circumendodermal band (CB), shape and number of vascular bundles and xylem contour. Results: Some characteristics of the petioles allow the grouping of species. The diagnostic features are: colour, presence/absence of wings, number of vascular bundles, bundles contour, xylem contour and presence/absence of CB. Conclusions: Petiole characters alone do not allow the identification of the taxa at specific level, although along with others they contribute to the systematics of the genus. The anatomy of the petiole does not show in general terms relationship with the habit of these plants. The type and distribution of subepidermic mechanical tissue and the presence of CB are associated with species that inhabit exposed and dry environments, but these features are not exclusive of the taxa that grow under these conditions. [ABSTRACT FROM AUTHOR]

We documented somatic and meiotic chromosome numbers of 6 species of Asplenium from Argentina. We present for the first time chromosome numbers of A. ulbrichtii var. serrato-dentatum, 2n=2x=72, and A. triquetrum, 2n=4x=144. Previously reported counts of n=72 for A. auritum, 2n=2x=72 for A. claussenii, n=36 for A. formosum, and 2n=8x=288 for A. serratum, were confirmed. [ABSTRACT FROM AUTHOR]

• Root anatomy contributes sometimes to taxonomy • Few phylogenetically related species share the same root subtype • Root anatomy is not related to plan habit Asplenium L. (Aspleniaceae) is a large fern genus whose systematics is based mainly in leaf and reproductive characters. In Aspleniaceae, the root anatomy allows delimit the two genera, Asplenium and Hymenasplenium Hayata. Various root subtypes are recognized in Asplenium, according to the layers and number of asplenium sclereids that constitute the inner cortex. In order to assess the potential use of root features in the taxonomy and the phylogenetic relationships within Asplenium, the roots of the 37 species inhabiting Argentina were studied. Observations were carried out employing light microscopy. Various root subtypes were registered. Only in few instances the root subtypes were shared by closely phylogenetically related species, being in the majority of cases homoplastic characters. The root subtype was not related to the plant habit. [ABSTRACT FROM AUTHOR]