Structure and Development of the Sporoderm in Coniogramme japonica (Thunb.) Diels (Hemionitidaceae)

The formation and development of the sporoderm of the fern Coniogramme japonica (Thunb.) Diels (Hemionitidaceae) was studied by means of light microscopy (LM),scanning electron microscopy (SEM),and transmission electron microscopy (TEM).Results indicated that the surface of the exospore was smooth.The exospore could be identified with two layers,a thinner inner layer and the thicker outer exospore.The perispore was also distinguished cleary into two layers,the outer perispore layer and the inner perispore layer.Radially arranged rodlets were also identified in the upper part of the perispore.The outer perispore showed a reticulated structure，composed of scales and spherules.The two layers of the perispore formed the surface ornamentations of the spore.The origin of the perispore of the fern Coniogramme japonica is discussed here and the results can provide information for palynologic and phylogenic research.