In the previous reports, the authors made a hypothesis that the dark-germination property of tobacco seeds (Nicotiana tabacum L.) is governed by double recessive genes (WATANABE et al. 1977 a, b, 1979). The purpose of the presernt paper is to verify that postulation by identifying the genotypes of F₂ plants from a cross between two supposed genotypes, AABB and aabb. A cross was made between a light-requiring variety, Kirigasaku and a light-indifferent variety, Xanthi. The former was assumed to have a genotype of AABB and the latter aabb. Sixty eight F₂ plants were allowed to self-pollinate or crossed with Xanthi. The seeds produced by the cross were called "test cross" seeds, and referred to as R₁F₁ seeds. As shown in Fig.1, by a dark-germination test of these two kinds of seeds F₂ plants could be classified into two groups. A group consisted of F₂ plants producing F₃ and R₁F₁ seeds which could not germinate under darkness (Group I). On the other hand, the remaining 39 F₂ plants produced F₃ Seeds showing varying degree of dark-germination ranging from 8.0 to 96.0 percent and R₁F₁ seeds from 22.0 to 97.0 percent (Group II).