Formation and Development of Sporoderm of Ceratopteris thalictroides (L.) Brongn. (Parkeriaceae)

The formation and development of sporoderm of the fern Ceratopteris thalictroides (L.) Brongn. (Parkeriaceae) were studied by means of light microscopy, scanning electron microscopy and transmission electron microscopy. The mature spores are radially symmetrical and trilete. The surface of spores is smooth and shows a rib-shaped (costate) ornamentation. The sporoderm consists of endospore, exospore and perispore. The exospore, which is formed by sporopollenint, is prominent; it is about 3-5 µm thick, and its rib-shaped ridges are about 5-7 µm high. The surface is smooth and the texture is uniform. The perispore is formed by the tapetal residues, which deposit on the outside of the exospore. The perispore is very thin, about 0.1 µm thick, with many small rod-like projections in the surface of perispore. The results will contribute to a better understanding of the origin, development and formation process of the sporoderm of ferns. They can also provide basic information about the palynology and phylogeny of ferns.