In electron-microscopic studies of fungi a structure which we term the lomasome ("border body") is shown in 9 genera representing the 3 major classes of the Eumycota. It appears to consist of an aggregation of vesicles or granules or both between the plasma membrane and the cell wall. While the function and composition of this structure is obscure it is nevertheless worthy of note in that at present it represents the only structure on the sub-cellular level which frequently occurs in the Eumycota and which thus far has not been reported from any other cell type.