Morphology and ultrastructure of the spores of the Grammitidaceae from Argentina

Spores of Grammitidaceae that grow in Argentina were studied, including Grammitis magellanica, G. patagonica, G. poeppigiana, Lellingeria tungurahue, and Melpomene peruviana. The study was performed on herbarium material with a light microscope and scanning and transmission electron microscopes. The spores are trilete with circular outline in polar view, the equatorial diameter is 30-83 μm and the polar diameter is 28-64 μm. The exospore is 0.3-1.44 μm thick, tuberculate-papillate, verrucate and in some cases gemmulate. It is composed of two layers and includes radial channels and very small cavities with dark contents. The cavities are in the exospore outer layer, mostly arranged along the contact surface with the inner layer. They are tangentially aligned with respect to the inner exospore surface. The perispore is c.a. 270 nm thick. It is composed of one to several strata and has irregular, spaced concentrations of dense materials. Globules of different sizes, free or fused together and covered with the perispore were observed. The sporoderm organization and structure are similar in the three genera studied. Nevertheless, differences in spore size, general morphology and the wall thickness were found.