Eusporangiate sporangia are characterized by
Eusporangia represent ancestral sporangial type observed in lycophytes, Psilotum, Tmesipteris, Equisetum, and eusporangiate ferns Ophioglossum, Botrychium, Marattia and Angiopteris. They develop from several initial cells producing several wall layers, thick multilayered wall, relatively large volume containing hundreds to thousands of spores, and generally lack specialized annulus with explosive mechanism, dehiscing via simple slit or apical pores. Leptosporangia contrast with single initial, thin wall, few spores and differentiated annulus for explosive dehiscence enabling efficient wind dis
Ref: Bower Classification of Ferns; Kramer & Green 1990 Fern morphology; Raven Ch 20