Nuclear bodies in the maturing egg cell of a fern, Pteridium aquilinum.

Nuclear bodies about 250 nm in diameter, and with a strong affinity for uranium and acriflavine, appear in the nuclei of maturing egg cells of Pteridium. Many enter well-defined evaginations of the nucleus. The nuclear bodies are almost wholly digested by Pronase, but are resistant to ribonuclease and deoxyribonuclease. Radioactive labelling gives no evidence of the presence of nucleic acids, but X-ray microprobe analysis indicates phosphorus. It is concluded that the bodies consist entirely of acidic protein, possibly phosphorylated. This protein may be a structural component of the nucleus, temporarily displaced and aggregated as a consequence of the fine dispersal of the chromatin.