The structure and mitotic behaviour of a nuclear inclusion in a fern.

A study has been made of the structure and behaviour during mitosis of a crystalline inclusion within cell nuclei of roots of Dryopteris filix-max. The inclusion within the interphase nucleus is an aggregate of randomly oriented crystals. All the crystals are similar, and consist of a cubic array of particles of unit spacing approximately 100 Å. During mitosis, the inclusions are eliminated from the nucleoplasm at prometaphase. The crystals reappear within the nucleus at early interphase by a process of random crystallisation from a preformed mass of amorphous material. The results are discussed in the light of previous work on nuclear inclusions in plants and of current theories of the mode of action of microtubules.