(d) : When a hybrid is produced by fusion of somatic cells of two varieties or species, it is known as somatic hybrid. The process of producing somatic hybrids is called somatic hybridization. First, the cell wall of the plant cells are removed then the protoplasts of the two cells are brought in contact and made to fuse by means of electrofusion or chemicals like polyethylene glycol $(PEG)$ and sodium nitrate. The fused protoplasts soon develop their own walls and are called somatic hybrids.