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• The ligular shape of eleven species is described for the first time. • The size of the ligule is related to the size of the supporting leaf. • Ligule rapidly reach their adult size and shape in young leaves. • Xerophytic and mesophytic species share ligular shapes and apex. The ligule is an important character in the taxonomic delimitation of Selaginella species. Here, the morphology of this organ is described in 11 American species. Four of these species are xerophytic: Selaginella convoluta, S. microphylla, S. peruviana , and S. sellowii , and seven are mesophytic: S. anceps, S. diffusa, S. flagellata, S. flexuosa, S. mollis, S. silvestris , and S. sulcata. Morphological data were obtained by traditional histological techniques. Observations were made by light and scanning electron microscopy. Variations in ligule size in vegetative leaves and sporophylls were determined using a correlation analysis with Spearman's coefficient. The ligule was found to have five body shapes: campanulate, linguiform, elliptic, fan-shaped, and rectangular. Each shape can have a lobed (bi-, tri-, or multi-lobed), rounded, or truncate apex. Size, shape, and apex are characteristic of each species and remain constant in young and mature leaves. No significant differences were observed between xerophytic and mesophytic species. The ligule of all species studied is described for the first time. Micrographs of all the species studied are presented, and the morphological results of this study have been mapped into the recent phylogeny of the genus. [ABSTRACT FROM AUTHOR]

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Copyright of Boletín de la Sociedad Argentina de Botánica is the property of Sociedad Argentina de Botanica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We studied the petiole structure of twelve American species of Pteris: P. ciliaris, P. cretica, P- deflexa, P. denticulata, P. ensiformis, P. exiguo, P. inermis, P. mvhifida, P. mutilata, P. quadrlaurita, P. tristicula and P. vittata, using both light and scanning electron microscopy. We found that petioles are characterized externally by the presence of an adaxial groove and two dorsal-lateral ventilation areas. Internally, petioles are monostelic V-, U- or inverted-fi-shaped axes. The vascular system is surrounded by one endodermis cell layer and 1-3 pericycle strata. We propose a classification of the vascular bundles into four types considering their shape, the shape of the xylem ends, the number of protoxylem zones and the presence of parenchyma bands in the xylem [ABSTRACT FROM AUTHOR]