Ultrastructural observations on Helvellaceae (Pezizales). Ascosporogenesis of selected species of Helvetia

Abstract

The ultrastructure of ascosporogenesis including observations on spore delimitation, primary wall deposition, and formation of the secondary wall is examined in three species of the genus Helvella. The double membranes delimiting the spores and the ascus plasmalemma stain identically with silver proteinate poststain. Primary wall formation is similar in all species examined, although very early development was observed only for H. macropus. Secondary wall formation, which results in the characteristic spore ornamentation, appears to be quite similar for the three species. In addition, observations are made on the structure and origin of the epispore and on cytological details of the epiplasm and sporoplasm relating to spore ontogeny.