NUCLEAR BEHAVIOR IN THE BASIDIOMES AND ECTOMYCORRHIZAS OF HEBELOMA-WESTRALIENSE SP-NOV

Hebeloma westraliense is described, and its identity as a new species established by comparison with other species of the genus. It formed ectomycorrhizas in aseptic and pot cultures with species of Eucalyptus and Allocasuarina, and basidiomes were produced in pot cultures with Eucalyptus camaldulensis, E. teretecornis and E. diversicolor. Septa in the stipe and pileus including those delimiting the basidium had clamp connexions, and cells in both juvenile and mature tissues were dikaryotic. Basidia were consistently quadrisporic and spores had two nuclei. In developing basidia a post-meiotic nucleus migrated into each spore, and a post-meiotic mitosis occurred in spores after septum delimitation but prior to morphological maturation. Mature spores should therefore be homokaryons and this view was supported by observations of spore germination. Mycelium produced by single spores was monokaryotic and without clamp connexions.