[Electron microscopic study of the developmental cycle of an actinomycete endosymbiont in the nitrogen-fixing nodules on the roots of Alnus glutinosa].

As has been shown by electron microscopy, the development of the endosymbiont in the nitrogen-fixing nodules of A. glutinosa proceeds either along the known (hyphae leads to vesicles) or less convenient pattern (hyphae leads to sporangia leads to spores). The paper presents more complete information about the structure of layers which separate the endosymbiont from the cytoplasm of host cells and about changes in the structure of the both partners accompanying sporogenesis.