Abstract: Root nodules of five species of Elaeagnus were studies under the light microscope. Elaeagnus pungens Thunb. and Elaeagnus sp. (introduced from Vietnam) were further investigated by electron microscope. The endophytic organism of Elaeagnus pungens Thunb. has three different developing stages. In the mature nodules, the main form is the vesicle. The hyphae forming the vesicle consist of septate, branching, terminal swollen filaments. The organism appears to be an Actinomycete. In some cases, bacterieid-like cells have also been observed. They might have arisen from the hyphae. The role played by the different forms of the endophyte in symbiotic nitrogen fixation is also discussed.