296 The Living Plant 



like those of one of the parents and quite free from the green of 

 the other. These hybrids, when grown, were also self-fertilized, 

 and produced a large number of offspring; and as a result a re- 

 markable fact came to light, namely, that although approxi- 

 mately three-fourths (75%) of these plants possessed yellow 

 cotyledons, one-fourth (25%) had green cotyledons just like those 

 of one of the grandparents. Furthermore, when these green- 

 cotyledoned forms were propagated by self-fertilization, all of 

 their numerous offspring had green cotyledons, and never yel- 

 low, which color was thus permanently bred out of these plants 

 and their descendants. But when the 75% of yellow-cotyledoned 

 forms were self-fertilized, their offspring gave this striking result, 

 that one-third of them (and therefore one-fourth, or 25%, of the 

 entire original number in this generation) produced only yellow- 

 cotyledoned kinds, as did their offspring, and theirs again indefi- 

 nitely, the green being thus bred permanently out of these forms 

 and their descendants. But the remaining two-thirds of the yellow 

 kind (forming half, or 50%, of the total number), acted, when 

 self-fertilized, precisely as their parents had done, producing 25% 

 green, and 75% yellow kinds of which latter 25% bred perma- 

 nently yellow; and the same thing was repeated in the next genera- 

 tion, and so on without limit. The method of this distribution of 

 characters in the offspring is shown graphically in the accom- 

 panying diagram (figure 105), in which, however, the exigencies 

 of printing forbid the use of color, for which reason the yellow 

 cotyledons are represented by the solid black circles, and green 

 by the white ones. Moreover, the first generation, (and half 

 of the later individuals) though themselves possessing yellow 

 cotyledons as a visible or so-called dominant character, have 

 obviously the power of transmitting the green as an invisible or 

 recessive character; and this fact is represented in the diagram by 

 giving to those individuals a white center. It is not yet wholly 

 clear, by the way, why Peas which have the power of transmitting 

 both yellow and green cotyledons should always have yellow ones; 



