Spore morphology and ultrastructure of Dennstaedtiaceae from Paranaense Phytogeographic Province I.: genus Dennstaedtia

• Perispore ornamentation characterizes groups within Dennstaedtia.
• Exospore characteristics are common for all species of Dennstaedtia.
• Spores are a useful tool to identify herbarium specimens.
• The types of ornamentation are unrelated to the geographical distribution of species.

The spore morphology and wall structure of Dennstaedtia species from the Phytogeographic Paranaense Province: Dennstaedtia cicutaria, D. cornuta, D. dissecta, D. globulifera, D. obtusifolia were studied using light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The spores are trilete, brown, triangular in polar view and plane-hemispheric to plane-convex in equatorial view. The exospore is homogeneous, with two layers. The perispore has an alveolar structure and is composed of one or two layers. The outer perispore surface bears the sculpture, which has elements of varied shapes (verrucae, ridges, reticles), an different sizes and fusion. This variation allows characterize species or groups of species. Three different types of perispore ornamentation can be found: 1. Verrucate with verrucae covered with rodlets; 2. Verrucate-rugate with verrucae and smooth ridges; 3. Reticulate. The spores constitute an important source of characters with a systematic value for the genus Dennstaedtia and they are a useful tool for the identification of herbarium samples.