Abstract: A special structure which originates from the nucleolus and persists during mitosis is observed in meristematic cells of Vicia faba, and is called nucleolar residual in this paper. The result of conventional staining showed that the nucleolar residual (NR) was a medium electron-dense structure that could be distinguished from chromosomes. At the end of prophase, the NR was observed in the dispersing nucleolar material, which consisted principally of granules and fibrils about 15 to 20 nm in diameter. In prometaphase, the NR, composed mainly of the similar granules and fibrils, was found attached to chromosomes. Results of Bernhard's technique for RNP (ribonucleoprotein) preferential staining indicated that the main chemical component of the NR was RNP, and sometimes bleached regions showing the same reaction as chromatin in Bernhard's staining appeared in the structure. In metaphase and anaphase some of the NRs were attached to chromosomes while others existed randomly in the cytoplasm. The NR is supposed, according to its cytochemical features and its behavi0ur during the nucleolar disintegration, to be a structure composed mainly of nucleolar matrix material or nucleolar skeleton.

Key words: Nucleolar residual, Nucteotar-matrix, 'Persistent nucleoli, ,Vicia faba