Fine Structure of Mycota

Though the dictyosome of the Golgi apparatus appears to be generally distributed in plant and animal cells, it is here described for the first time in the fungi. The present report illustrates, in electron micrographs of thin sections, the characteristic structure of the Golgi dictyosome in a special cell type of a supporting pseudo-tissue (the inner ectal excipulum) of a highly evolved Ascomycete, Neobulgaria pura (Fr.) Petrak, a monotypic discomycete. This organelle may secrete the gelatinous matrix filling the cup formed by the inner ectal excipulum. All the other cells in this species appear more typical of fungal cells; i.e., they have no dictyosome and, unlike the cup-forming cells, they show characteristic continuities of the plasma membrane with the perinuclear cisternae. The dictyosome, in those cells in which it appears in this fungus, is formed by a series of vesiculations of the outer component of the nuclear envelope that align to form a stack of sacs. The sacs near the nucleus are flattened (by what appears to be an intermembrane cement) while those near the plasma membrane are more distended. These observations suggest three possibilities: first, fungi may be more closely related to other eukaryotic cells than previously suspected from electron microscopic studies; second, the outer nuclear membrane may have been the primitive precursor of the dictyosome; and third, the inverse relationship of the occurrence of the nuclear membrane plasma membrane continuities and the dictyosome suggests that the latter may have evolved as a means of removing from the cell the products of reactions occurring on a discontinuous membrane system.