The author treated genetically a race of Celosi a cristala L. with inflorescencesbeing mosaic of scarlet and yellow. Self-pollinated seeds of mosaic individuals were found, in general, to yield a progeny consisting of self-scarlet, mosaic and self-yellowindividuals; neverthless in the majority of cases the rate of appearanceof the self-scarlet was higher in the progeny from the scarlet parts ofthe mosaic inflorescences than from theself-yellow parts of them; andin a few cases there was no remarkable difference in the rate of segregationfor the inflorescence-colour between the progenies of the scarletparts of mosaic inflorescences and of the yellow parts of the same. There were two types of self-scarlet individuals which derived fromthe mosaic strain: homo-self-scarlets and hetero-self-scarlets; and thehomo type ones in no instance segregated. By self-pollination the apparently-self-yellow ones produced in themajority of cases some self-scarlets and mosaics besides parental selfyellows;the ratios of those three were very variable. Yet the authorstarting from an apparently-self-yellow which descended from a mosaic, by repeated self-pollinations for several generations, obtained a fixedself-yellow strain. The results of the crossing experiments between homo-self-scarletsand self-yellows, namely the cases of F1, F2, F3 and back-crossings, could be explained as a case of Mendelian monohybrid, when the selfyellowsand mosaics were arrayed as one party against the seif-scarlets. The abovementioned facts can be explained on the basis of the following assumption: Regarding the appearance of flower (inflorescence)-colour, there are two genes which are allelomorphic to each other. One of the genes A, producing scarlet colour, is dominant and the other a, producing yellow colour, is recessive. And A is stable and a is unstable; namely, in some occasions there take place gene-mutations a→A, but never A→a. The homo-self-scarlet individuals are AA, the hetero-self-scarlet individuals are Aa and the self-yellow individuals are aa. Sometimes parts of tissues of self-yellow individuals, being caused by gene-mutation a→A, can be modified into scarlet. The mosaic individuals are thus derived from self-yellow ones.