234. A TEXTBOOK OF GENERAL BOTANY 
white flowers. When, however, pink-flowered plants are self- 
fertilized, they will, like their pink-flowered parents, again pro- 
duce red-flowered, pink-flowered, and white-flowered plants in 
the ratio of one red, two pink, and one white. The inheritance 
of the flower color in this plant, and its explanation in terms of 
factors and chromosomes, is shown in Fig. 232. The flowers 
represent plants; A, a chromosome carrying a factor for red ; 
W, a chromosome with a factor for white. Circles represent 
gametes (sexual cells). 
The explanation of color inheritance in the four-o’clock is as 
follows: A red-flowered plant has two chromosomes, each with 
a factor for red. During the reduction division these segregate 
so that the gametes possess only a single chromosome with a fac- 
tor for red. Likewise, a white-flowered plant has two factors 
for white, while a gamete produced by a white-flowered plant 
carries only one such factor (line 1, Fig. 232). 
The hybrid (known as the F,, or first filial, generation) is 
therefore produced by the union of a gamete with a chromo- 
some carrying a factor for red and a gamete having a chromo- 
some with a factor for white. The result is that the hybrid 
possesses both a factor for red and one for white, and is pink- 
flowered (line-2, Fig. 232). When this individual gives rise to 
gametes, these will be of two kinds, some with a chromosome 
bearing a factor for red and others with a chromosome bearing 
a factor for white. Just as the chromosome carrying the factor 
for red and that with the factor for white came together in the 
fertilized egg, so they again separate before the formation of 
gametes. The generation (/,) formed as a result of the union 
of the gametes produced by the #, hybrids is shown in Fig. 232. 
If a male nucleus with the factor for red fertilizes an ege with 
the factor for red, the result will be a plant which has two fac- 
tors for red in all its vegetative cells and which will produce 
red flowers. Likewise, if a male nucleus with a factor for white 
fertilizes an egg with a factor for white, the fertilized egg will 
have two factors for white and the plant will produce white 
flowers. When, however, a male nucleus with a factor for white 
