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The occurrence of helical cell wall thickenings in fern roots is not well investigated and there are few records about it in the literature. To assess the presence of thickenings and their chemical composition, we studied all species of Polypodiaceae, which grow in northwestern Argentina, using light microscopy, scanning electron microscopy, and fluorescence microscopy. Twenty of the twenty-one species studied showed the thickening in the roots. Only in Melpomene peruviana are helical cell wall thickenings absent. All thickenings have cellulose as the main compound. The structure of the thickening may be classified as simple, furcate, or anastomosing. All data presented in this paper corroborate the same structure and chemical composition of thickenings previously reported for Aspleniaceae. [ABSTRACT FROM AUTHOR]

The circumscription of the genus Cheilanthes Sw. is supported by molecular and morphological characters; nevertheless, the taxonomic status of some species remains uncertain because they have not been molecularly tested yet. This study analyzes the belonging of Cheilanthes volcanensis de la Sota to this genus, since this species was treated with doubts about its generic identity. From a morphological approach, C. volcanensis is close to Cheilanthes species with pentagonal and highly divided leaf blades; petioles and rachises castaneous to black, glabrous, usually grooved adaxially; features that are also largely representative of the morphological circumscription of the genus Gaga Pryer, F.W. Li & Windham. The molecular analysis of a recent collection, identified a priori as C. volcanensis, demonstrated with high support that the species belongs to the genus Cheilanthes s. str., as was described originally. Finally, morpho-anatomical observations of this species and related species are also provided, which support its phylogenetic position and contribute to the correct generic delimitation of Cheilanthes s. str. [ABSTRACT FROM AUTHOR]

The pantropical fern genus Pteris L. has about 250 species of which 60 occur in the American continent. We studied the morphogenesis of the gametophyte, and the morphology of the young sporophytes of four species: P. cretica, P. ensiformis, P. multifida and P. vittata, together with a palynological analysis that includes the ability of spores to germinate. Gametophytes were obtained trough in vitro culture techniques with agar-gellified Knudson medium. Young sporophytes were placed in earth-sand (3:1) sterile substrate. We used light and SEM microscopy. Triletes spores predominate, but monolete, tetralete, and other types of apertura are often found. The viability of spores is not affected by the variation, so the term spore polymorphism is applied to the condition occurring among these species. Spore polymorphism is similar in P. cretica and P. multifida. Germination occurs following the Vittaria type, 3-7 days after the sowing. Filamentous, 3-5 celled gametophytes were found in P. cretica, P. multifida and P. vittata, and 7-9 celled in P. ensiformis. Development of gametophytes takes place following Adiantum type and Ceratopteris type. The symmetry of the laminae differ in gametophytes, those of P. ensiformis and P. multifida are similar and differ from the other two species, P. cretica and P. vittata. Gametophytes of P. ensiformis, P. multifida and P. vittata are bisexual and protandric, while male gametophytes were found in P. cretica. Antheridia correspond to the common leptosporangiate type; they are cylindric in P. vittata and ovoid in the other three species. Archegonia necks have 4 rows of 4 cells each. The sporophytes complete their development 3 months after sowing, and have indument close to the adult plants. P. cretica shows obligated apogamy.