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The leaf morphology of Selaginella species from subtropical South America show differences in structure and ultrastructure that are useful for species identification. We studied the following epidermal traits: micromorphology of stomatal types, distribution patterns of silica cells, silica cells and silica bodies of Selaginella convoluta, S. microphylla, S. sellowii and S. sulcata, using light and scanning electron microscopy. Five stomatal types were observed, anomocytic, actinocytic, anisocytic, staurocytic and tetracytic and two additional variants, anomodiacytic and anomoparacytic. Five silica cell distribution patterns were identified, laminar, medial, medial-basiscopic, subcostal, and submarginal. Pyramidal silica bodies and conical bodies with concave base are described for the first time. In the studied species, silica bodies are pyramidal in S. convoluta and globular, conical and pyramidal in S. microphylla, whereas in S. sellowii and S. sulcata they are conical, with concave base of different sizes. Illustrations of the epidermal features, LM photographs, SEM micrographs and comparative tables are presented.

Serpocaulon triseriale (Sw.) A.R. Sm. is considered the most widespread species in the genus. It has been recorded from south of Mexico to Bolivia, Paraguay and Brazil. Here, we expand its distribution by reporting a new record from Salta province, Argentina, based on material that was previously misidentified as S. polystichum (Link) A.R. Sm. We compare the S. triseriale and S. polystichum with their relatives (S. attenuatum (Humb. & Bonpl. ex Willd.) A.R. Sm., and S. rex Schwartsb. & A.R. Sm.), providing photographs of the plants in the field, SEM images of the spores and light photos of the rhizome scales to discriminate S. rex from S. triseriale. In addition, distributional records are included.