Abstract
Microspores extracted from isolated sporophylls assigned to Lepacyclotes (syn. Annalepis) zeilleri from the Ladinian (Middle Triassic) of northeastern France are described and studied in transmitted light as well as with help of scanning and transmission electron microscopes. These spores, which are monolete and cavate, correspond to Aratrisporites saturni if found as sporae dispersae. Their ultrastructure is quite comparable with that of microspores of other Triassic lycopsids as well as modern Isoetes testifying to a close relationship between the parent plants. Indeed, their exospores possess laminated zones (LZ) in the apertural area. A review of the lycopsids indicates that the laminated zones existed as early as in the Devonian and that they remained unchanged since then. Thus, this feature is considered a fundamental evolutionary character of the lycopsids. However, our analysis of the laminated zones also suggests that they were devices involved in the aperture functioning among which the control of hydration and dehydration mechanisms.
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