THE ULTRASTRUCTURE OF SCHOPFIPOLLENITES: ORBICULES AND TAPETAL MEMBRANES

Abstract

Electron microscopy of in situ fossil (Pennsylvanian) pollen assignable to the taxon Schopfipollenites indicates the presence of orbicules and tapetal membranes similar to those associated with the secretory tapetum of extant plants. Orbicules are spheroidal, hollow and associated with a complex tapetal membrane system. Each membrane is three‐parted, consisting of two thin layers attached by beads of electron‐dense material. A thicker, outer layer is suggestive of the orbicule reticulum described in some angiosperm families. A comparison between the fossil orbicules and membrane systems and those of extant plants is presented.