MENDEL 



each generation is seen by the follow- 

 ing summary, in which A and a denote 

 again the two parental characters, and 

 Aa the hybrid forms. For brevity's 

 sake it may be assumed that each plant 

 in each generation furnishes only 4 

 seeds. 



2"— 1 : 2 



2"-l 



In the tenth generation, for instance, 

 2» — 1 = 1023. There result, therefore, 

 in each 2,048 plants which arise in this 

 generation 1,023 with the constant 

 dominant character, 1,023 with the re- 

 cessive character, and only two hy- 

 brids. 



THE OFFSPRING OF HYBRIDS 



IN WHICH 



SEVERAL DIFFERENTIATING 



CHARACTERS ARE ASSOCIATED 



In the experiments above described 

 plants were used which differed only 

 in one essential character. ^^ The next 

 task consisted in ascertaining whether 

 the law of development discovered in 

 these applied to each pair of differ- 

 entiating characters when several di- 

 verse characters are united in the hy- 

 brid by crossing. As regards the form 

 of the hybrids in these cases, the 



15 [This statement of Mendel's in the light 

 of present knowledge is open to some mis- 

 conception. Though his work makes it evi- 

 dent that such varieties may exist, it is very 

 unlikely that Mendel could have had seven 

 pairs of varieties such that the members of 

 each pair differed from each other in 07jly 

 one considerable character (wesentliches 

 Merkmal). The point is probably of little 

 theoretical or practical consequence, but a 

 rather heavy stress is thrown on ^^wesent- 

 lichn 



11 



experiments showed throughout that 

 this invariably more nearly approaches 

 to that one of the two parental plants 

 which possesses the greater number of 

 dominant characters. If, for instance, 

 the seed plant has a short stem, termi- 

 nal white flowers, and simply in- 

 flated pods; the pollen plant, on the 

 other hand, a long stem, violet-red 

 flowers distributed along the stem, and 

 constricted pods; the hybrid resembles 

 the seed parent only in the form of the 

 pod; in the other characters it agrees 

 with the pollen parent. Should one of 

 the two parental types possess only 

 dominant characters, then the hybrid 

 is scarcely or not at all distinguishable 

 from it. 



Two experiments were made with a 

 considerable number of plants. In the 

 first experiment the parental plants 

 differed in the form of the seed and in 

 the colour of the albumen; in the sec- 

 ond in the form of the seed, in the 

 colour of the albumen, and in the 

 colour of the seed-coats. Experiments 

 with seed characters give the result in 

 the simplest and most certain way. 



In order to facilitate study of the 

 data in these experiments, the different 

 characters of the seed plant will be 

 indicated by A, B, C, those of the 

 pollen plant by a, b, c, and the hybrid 

 forms of the characters by Aa, Bb, and 

 Cc. 



Expt. l.—AB, seed parents; 



A, form round; 



B, albumen yellow. 

 ab, pollen parents; 



a, form wrinkled; 



b, albumen green. 



The fertilised seeds appeared round 

 and yellow like those of the seed pa- 

 rents. The plants raised therefrom 

 yielded seeds of four sorts, which fre- 

 quently presented themselves in one 

 pod. In all, 556 seeds were yielded by 

 15 plants, and of these there were: 



