Development of the sporangia and associated structures in Schizaea pectinata (Schizaeaceae : Pteridophyta)

Abstract

A light microscope study of the initiation of the frond and sporangial development in Schizaea pectinata revealed that sporangia arose from single-celled initials in marginal positions on narrow, strap-shaped pinnae. The sporangia were displaced to a superficial position by marginal development of a false indusial (pseudoindusial) structure. Divisions of a single, central initial with four cutting faces produced the archesporial tissue and a two-layered tapetum that differentiated into a combination tapetum consisting of an outer, cellular parietal tapetum and an inner, plasmodial tapetum that was intimately associated with the archesporial tissue and later with the developing spores. Mature sporangia had an apical annulus consisting mainly of a single tier of cells that differentiated from the layer of cells forming the sporangium wall. Thirty-two spore mother cells were produced and if no abortion occurred, approximately 128 spores developed within each sporangium. Key words: Schizaea pectinata, sporangial ontogeny, parietal tapetum, plasmodial tapetum, combination tapetum.