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SynopsisThe structure and diversity of fern spores, based on SEM studies, are assessed in relation to general evolutionary trends and systematics. A review of spores of myrmecophytic ferns includes SEM figures of eight species and the ant Iridomyrmex cordataus. The diversity, especially in Lecanopteris spores, is correlated with other characters indicating systematic differences of the species. Convergence is shown in the echinate spores of the neotropical Solanopteris and those of the paleotropical Drynaria and Selliguea. Evidence for adaptation of spore structure to transport by ants is especially clear in the development of filamentous elements, unique among pteridophytes, in Lecanopteris mirabilis. These demonstrate an unusual labile nature of the wall, and provide insight into the functional role of intricate surface formation of spores.

First record is made of a dioecious condition in the heterosporous, terrestrial fern Plaiuzoma microplujllum R. Br. from northern Australia. The spores, gametophytes and young sporophyte are described and the role of heterospory and dioecism in these plants is discussed. The genus is newly classified as a subfamily Platyzomatoideae iu the Polypodiaceae.