Homology Assessment of the Boundary Tissue in Fruiting Bodies of the Lichen Family Sphaerophoraceae (Lecanorales, Ascomycota)

Abstract: The ascoma ontogeny of the family Sphaerophoraceae is reviewed. The development of the boundary tissue in Leifidium tenerum is described and compared with similar structures in some other mazaediate representatives of the family ( Sphaerophorus globosus, Bunodophoron dodgei and B. diplotypum ), and with the non-mazaedia-producing genera Austropeltum and Neophyllis. The dominant structure in the base of mature ascomata in all genera is a boundary tissue forming the border between ascomatal ("generative") and thalline ("vegetative") tissue. In the mazaedia-forming genera, the boundary tissue is composed of two layers. The upper layer is a zone of ascogenous hyphae, homologous to similar zones in Neophyllis and Austropeltum. The lower layer is a pseudoparenchymatic and often strongly pigmented zone formed by generative tissue, homologous to a zone of generative tissue present in Neophyllis but lacking in Austropeltum.