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The lycophyte genus Selaginella has a worldwide distribution with ca. 800 species. The genus is heterosporous and has ornamentation on the surface of both the megaspores and the microspores. Selaginella megaspore ornamentation is highly variable in both its macro- and microsculpture. Megaspore ornamentation is a species-specific morphological feature that can be used reliably for specimen identification. We present the first investigation of the megaspore surface of all 19 Selaginella species known from the state of São Paulo, Brazil, using scanning electronic microscopy (SEM). This study also includes Selaginella species that are invasive in Brazil. Based on the SEM analysis and high-resolution photographs, we provide detailed megaspore descriptions and an identification key for all species from São Paulo state. We also describe the proximal and distal pole ornamentation of the megaspores as well as the form and proportions of the trilete aperture.
One of the challenges when working with the genus Isoëtes is the scarcity of in-depth comparative analyses of its morphological characters. This paucity of analyses relates in part to the long-held conclusion that most of the characteristics associated with the traits of the genus aside from spore morphology, are too variable to be informative. As a result, our understanding of morphological variability among species of Isoëtes is underdeveloped. Recent workers have attempted to address this deficiency by examining the glossopodia of the ligule, a structure unique among living taxa to Isoëtes and its sister genus, Selaginella. The glossopodium is embedded in the adaxial surface of the microphyll, and has shown evidence of interspecific variability in the few studies in which it has been examined. However, these prior works were limited to qualitative comparisons. The present study compares 3D reconstructions of the glossopodia of three species, Isoëtes howellii, I. bolanderi and I. nuttallii, using morphometric analyses in addition to more traditional qualitative comparisons. MANOVA of measurements obtained from 3D reconstructions of the glossopodia show significant differences in size while elliptical Fourier analysis of these reconstructions demonstrates differences in shape among the species. These analyses provide a repeatable, statistical framework for future work on the glossopodium and potentially other traits in Isoëtes.
Based on newly collected plant material from Swedish Lapland a new name, Equisetum ×lapponicum, is proposed for the hybrid between E. scirpoides and E. variegatum. Macromorphological as well as micromorphological characters are presented in comparison with the parent species. The nomenclatural history of the hybrid combination is discussed in detail referring to older but invalid names used in the literature. An updated overview of reticulate evolutionary processes in subgenus Hippochaete at a global scale is presented.
We review the nomenclature of Selaginella polymorpha Badré, endemic to Madagascar, and conclude that this name is illegitimate by superfluity under the International Code of Nomenclature. The name should be rejected and replaced by the older S. pectinata Spring, coined in 1843.
Populations of Adiantum growing on serpentine barrens in Pennsylvania and Maryland have been identified as A. aleuticum (Rupr.) C.A.Paris ( = A. pedatum L. var. aleuticum Rupr.). This species, and the allopolyploid A. viridimontanum C.A.Paris, are known from serpentine in New England and Canada. A phylogenetic analysis based on two plastid markers showed that the Pennsylvania and Maryland populations are A. pedatum sensu stricto rather than A. aleuticum or A. viridimontanum.