Abstract The spore morphology and wall ultrastructure of 12 species of Ctenitis from Southern Cone of America were studied using light microscope, scanning and transmission electron microscope. The study was carried out with herbarium material from Argentine and Brazilian institutions. Equatorial diameters, polar diameters and laesura length were measured. The spores are monolete with echinate or folded ornamentation. In the echinate type, the spines are conical, with broad base and attenuate apex. In the rugate type, the folds are inflated, linear, sinuous, subglobose or handle-shape. The perispore surface is scabrate, rugulate, microverrucose or psilate. Stratification and ultrastructure in the species analyzed are very similar. The exospore is smooth and two-layered in section. Simple and branched channels are observed mainly in the outer exospore. The perispore is composed of two layers, the inner one forms the ornamentation and the outer covers all the outer and inner surfaces. Immature spores were found in all samples of C. fenestralis. The characteristics of the studied spores like macro-ornamentation, color and fold length provide relevant information to differentiate some species or groups of species within the genus.

Summary Background and aims : The morphological characteristics of the spores provide information for the identification of fern taxa. To deepen the analyses of the morphological characteristics of the spores of the isosporated ferns inhabiting the Punta Lara Nature Reserve using light microscopy. M&M : The spores of the isosporate ferns that grow in the Punta Lara Nature Reserve (Buenos Aires Province, Argentina) were studied under a light microscope. The study was carried out with fresh materials collected during three years (2016-2018) at different sites of the Reserve. Twenty fern taxa, 16 native and 4 exotic, were analysed. The registered characteristics were: colour, shape, major and minor equatorial diameters, polar diameter, length and characteristics of the laesura and wall ornamentation. Results : The colour of the spores may be yellow, light brown, dark brown and only in Equisetum they are green (chlorophyllous). Most spores are monolete (13 species), other trilete (6 species) and only one species has alete spores. The spore walls may be smooth, wrinkled, folded, verrucated, tuberculated, reticulated and winged. Conclusions : The morphology of the spores allows the identification of the ferns of the Reserve at a generic and specific level and provides information for palaeopalynological and aeropalynological studies and of soil spore banks.

Resumen Introducción y objetivo : Las características morfológicas de las esporas brindan información para la identificación de taxa de helechos. Profundizar los análisis de las características morfológicas de las esporas de los helechos isosporados que habitan en la Reserva Natural de Punta Lara utilizando microscopía óptica. M&M : Se estudiaron con microscopio óptico las esporas de helechos isosporados que crecen en la Reserva Natural Punta Lara (provincia de Buenos Aires, Argentina). El estudio fue llevado a cabo con material fresco colectado durante 3 años (20162018) en diferentes sitios de la Reserva. Se analizaron 20 taxa de helechos, 16 nativos y 4 exóticos. Las características registradas fueron: color, forma, diámetros ecuatoriales mayor y menor, diámetro polar, longitud y características de la lesura y ornamentación de la pared. Resultados : El color de las esporas puede ser amarillo, castaño claro, castaño oscuro y solo en el caso de Equisetum son verdes (clorofílicas). La mayoría de esporas son monoletes (13 especies), otras triletes (6 especies) y una sola especie posee esporas aletes. Las paredes de las esporas pueden ser lisas, plegadas, verrucosas, tuberculadas, reticuladas y ruguladas-crestadas. Conclusiones : La morfología de las esporas permite la identificación de los helechos de la Reserva a nivel de género y especie y aporta información para estudios paleopalinológicos, aeropalinológicos y de bancos de esporas del suelo.

O gênero Lygodium Sw. é um das poucas samambaias trepadoras no mundo. Os esporos de L. venustum Sw. e L. volubile Sw. foi estudados com microscopias de luz e eletrônicas de transmissão e varredura. Este trabalho é baseado em material de herbário. Os esporos são trilete, triangular com lados retos para convexo em vista polar. O equatorial diâmetro é 72-104 µm e o diâmetro polar é 64-84 µm. O ornamentação em L. venustum é verrucose-tuberculoso enquanto em L. volubile é verrucose-tuberculoso no proximal cara e com poucos cume no distal cara, em que um micro-ornamentação constituída por verrugas e tubérculos é observado. Um cume equatorial também está presente. O exosporo é de dois camadas, em L. venustum é liso em contraste com o exosporo ornamentado de L. volubile. O perisporo é similar nas duas espécies analisadas. Esta parede é de quatro camadas com elementos particulares dispostas radialmente na camada do meio. Nas superfícies de esporos de ambas espécies poucos spheroids é observado. Os resultados apresentados no presente estudo podem ser útil para o sistemática do gênero bem como para propósitos filogeneticos.

The genus Lygodium Sw. is one of the few climbing ferns in the world. The spores of L. venustum Sw. and L. volubile Sw. were studied using light, scanning, and transmission electron microscopy. This work is based on herbarium material. The spores are trilete, triangular, with straight to convex sides in polar view. The equatorial diameter is 72-104 µm, and the polar diameter is 64-84 µm. The ornamentation in L. venustum is verrucate-tuberculate while in L. volubile, it is verrucate-tuberculate in the proximal face but with a few ridges on the distal face, where a micro-ornamentation constituted by verrrucae and tubercles is observed. An equatorial ridge is also present. The exospore is two-layered; in L. venustum, it is smooth in contrast with the ornamented exospore of L. volubile. The perispore of the two species analyzed is similar. This wall is four-layered with particular elements arranged radially in the middle layer. On the spores surface of both species, few spheroids are observed. The results introduced in the current study may be useful for the systematics of the genus as well as for phylogenetic purposes.