ASPECTS OF PERMIAN PALEOBOTANY AND PALYNOLOGY .18. ON THE MORPHOLOGY AND ULTRASTRUCTURE OF POTONIEISPORITES-NOVICUS (PREPOLLEN OF LATE CARBONIFEROUS EARLY PERMIAN WALCHIACEAE)

The type species of the palynological form-genus Potonieisporites, P. novicus, can be considered to represent Late Carboniferous/Early Permi an conifers, assignable to the Walchiaceae of the Euramerican floral p rovince, Morphological and ultrastructural analysis of the species fal sifies earlier concepts of a monosaccate organization and the presence of a distal germinal area. The species is characterized by a monosacc oid sexine expansion, completely filled with an alveolate infrastructu re. A proximal aperture is distinct: but there is no evidence of dista l specializations indicative of the outgrowth of a haustorial pollen t ube; the species thus qualifies as prepollen. These characters are inc luded in an emended diagnosis for the species. A restricted concept of an exclusively walchiaceous status for the form-genus Potonieisporite s can not yet be proposed, mainly because of the lack of conclusive ev idence on the botanical affinity and the morphological/ultrastructural organization of similar pollen from the Gondwana floral province.