Plantlet composed of cells containing the double set of chromosomes.

The fusing germ cells of sexual reproduction contain only half the number of chromosomes compared to the fusion product. In the case of mosses and ferns this peculiarity of the chromosome set not only refers to some cells (as in the case of most other plants and animals). Moreover, cells containing the single set of chromosomes are forming a complete organism (the gametophyte, the lower, green part of the moss shown), alternating with the organism produced after germ cell fusion, which is containing the double set of chromosomes (the sporophyte, the upper yellow part of the moss shown).