Publications of various writers are cited showing that selective fertilization depending upon the genotype of the [male] gamete and the somatic cells of the style of the [female] parent has been found in Nicotiana, Zea, Rumex, Lychnis, Oenothera, certain of the Basidiomycetes and Phycomycetes. Both the mating of like with like or of unlike with unlike may be favored in any one case. The selection is due to an interaction between the genotype of the [female] diploid plant and the [male] gametophyte in higher plants or between the 2 gametes in Basidiomycetes. The degree of the selection varies greatly phenotypically as well as genotypically. The factors for selective fertilization are in some cases subject to relatively high mutability.