A PALAEOBIOLOGICAL DEFINITION OF SPOROPOLLENIN

Abstract

The term “spore” has been applied to single-celled and small multi-cellular propagules from a wide range of organisms. When the cell walls of these spores are encountered as fossils, there is no secure criterion of morphology for separating all algal spores from those of all vascular plants; nor of separating all pollen grains from micro- and isospores of vascular plants. The application of the term sporopollenin not merely to all these spores and pollen grains but also to kerogen and organic material in meteorites is questionable because of the biological origin implicit in the term. We need to know whether fossil organic matter other than spore and pollen exines has similar - or distinct - physico-chemical characteristics. Fossil spore wall material from diverse sources shows minor differences in physical properties such as specific gravity. Flotation on a density gradient may be one means of segregating such spores when differences of morphology alone are not sufficiently characteristic.