Sporeling development in Cavicularia densa was determined using controlled culture and light microscopy techniques. Ontogeny is typified by endosporic germination followed by early protonematal development via the production of a terminal quadrant of four cells which ruptures the spore wall distally. Sporeling production is triggered by the delimitation of a cuneate apical cell in one of the quadrants. Regular apical cell segmentation produces derivatives and adult merophytes that ultimately result in a juvenile Cavicularia gametophyte. The fundamental sporeling pattern exhibited by Cavicularia is shared only with that of its sister genus Blasia. Moreover, the patterns of sporeling and gemma/gemmaling ontogeny in Cavicularia and Blasia share quadrant systems of precise uniformity, thus reinforcing the close relationship between the blasialean genera.