Anatomical organization of Stoechospermum marginatum reveals small cortical cells with moderately dense cytoplasm, overlying a multilayered medulla comparatively poor in cytoplasmic contents. The anticlinal walls of cortical cells show local thickenings rich in alginic acids. Sori form on both thallus surfaces and show tetrasporangia, paraphyses and sterile-cells. The unicellular paraphyses are rich in sulphated polysaccharides whereas multicellular ones have abundance of not only polysaccharides, but also of vacuoles and phenols. The sterile-cells are modified cortical cells present on either side of the tetrasporangium and bear cytoplasmic strands towards soral cavity. Various stages of tetrasporogenesis are seen in a single sorus. The developing tetrasporangium shows a two layered wall, where the outer one is rich in alginic acid and inner has sulphated polysaccharides. An apical pad aids tetraspore release. Also involved in the release process are sterile-cells, paraphyses and polysaccharides.