Variation and Heredity 281 



together, there are produced two kinds of individuals, A's 

 and B's, of which there are three times as many A's as B's. 

 It has been found, however, that some of these A's are pure 

 forms, as indicated by the A on the left in our table, while 

 the others, as shown by their subsequent history, are hybrids, 

 A{B). There are also twice as many of these A(B)'s as of 

 the pure A's (or of the B's). Thus the results are really the 

 same as in our imaginary case, only obscured by the fact that 

 the A's and the A(B)'s are exactly alike to us in respect to 

 the character chosen. We see also why there appear to be 

 three times as many A's as B's. In reality the results are 

 1 A, 2 A{B), 1 B. 



In subsequent generations the results are the same as in 

 this one, the A's giving rise only to A, the B's to B, and the 

 A(B)'s continuing to split up into the three forms, as shown in 

 our diagram. Mendel found the same, Taw, to hold for all the 

 characters he examined, including such different ones as the 

 form of the seed, color of seed-albumen, coloring of seed-coat, 

 form of the ripe pods, position of flowers, and length of stem. 



Mendel also carried out a series of experiments in which 

 several differentiating characters are associated. In the first 

 experiment the parental plants (varieties) differed in the form 

 of the seed and in the color of the albumen. The two char- 

 acters of the seed plant are designated by the capital letters 

 A and B ; and of the 'pollen plant by small a and b. The 

 hybrids will be, of course, combinations of these, although 

 only certain characters may dominate. Thus in the experi- 

 ments, the parents are AB (seed plant) and ab (pollen plant), 

 with the following seed characters : — 



Seed parent J A form round Pollen parent | a form angular 



AB \ B albumen yellow ab \ b albumen green 



When these two forms were crossed the seeds appeared round 

 and yellow like those of the parent, AB, i.e. these two char- 

 acters dominated in the hybrid. 



