In somatic hybridization, the fusion of protoplasts from different plant varieties or species is a key technique. Protoplasts are plant cells that have had their cell walls enzymatically removed, exposing the cell membrane. This condition allows for the direct fusion of cellular contents including the nucleus and cytoplasm from different cells, facilitating recombination and the formation of a hybrid cell. The process of fusion typically involves techniques such as electrofusion or chemical treatments to encourage the protoplasts to merge.

Looking at the options provided:

• Option A: Callus – This is not correct. A callus is a mass of unorganized plant cells that are generally not involved in fusion during somatic hybridization but are rather a product of the culture of somatic cells.
• Option B: Somatic embryos – These are not the direct subjects of fusion in somatic hybridization. Somatic embryos can develop from hybrid cells, but they themselves are not fused; they are derived from somatic cells under appropriate conditions.
• Option C: Protoplasts – This is correct. Protoplasts are indeed what are fused in somatic hybridization to combine the genetic material from two different plants or varieties.
• Option D: Pollens – These do not fuse in somatic hybridization. Pollen fusion is more relevant to sexual reproduction and breeding, not somatic cell procedures.

Therefore, the correct answer is Option C: Protoplasts.