The stomatal ontogeny and structure of the liassic pteridosperm Sagenopteris (Caytoniales) from Hungary

Stomatal ontogeny is often inferred but rarely documented for extinct fossi l plants because it requires observations from young leaves that are rarely preserved as fossils. The discovery of several very young leaves of the Ju rassic plant Sagenopteris (Caytoniales) in the Mecsek Mountains (southern H ungary) in a good state of preservation provides the opportunity for studyi ng the stomatal ontogenesis of this genus. The specimens show perigenous an omocytic stomata. This feature confirms the evolutionarily high position of Sagenopteris among fossil gymnosperms and supports the opinion that the an cestors of angiosperms and some groups of pteridosperms might be closely re lated. Such clear examples of stomatal development have not previously been documented for fossil material.