300 BEITISH PLANTS 



de Vries unearthed them in 1896 and published them in 

 1901. Mendel selected the pea for two reasons: (1) be- 

 cause the flowers are self-fertilized and therefore under 

 experimental control; (2) because they exhibit numerous 

 characters which breed true — an almost ideal state of 

 things for the purpose. Mendel marked out for experi- 

 ment a certain number of differentiating characters and 

 investigated their inheritance separately. Crosses were 

 made between taU and dwarf varieties, coloured seed- 

 coats and white, white and purple flowers, yellow and 

 green-coated seeds, smooth and wrinkled seeds, etc. 

 However the cross was made it was found that aU the 

 plants obtained by sowing these hybrid-seeds exhibited 

 one only of each pair of contrasted qualities. The one 

 quality so exhibited he caUed Dominant, and the other, 

 which was apparently suppressed, the Recessive. Thus 

 on crossing tall plants with dwarf, aU the subsequent 

 plants were taU. In the hybrids, therefore, tallness is 

 dominant and dwarfness recessive. The seeds of this 

 generation, produced by seM-fertilization, were sown and 

 both taUs and dwarfs appeared among the plants obtained. 

 The latent character, dwarfness, had thus reappeared 

 in the second generation, and that in the proportion of 

 1 to 3. No intermediate forms occurred. On sowing 

 the seeds of the second generation, obtained as before 

 by self-fertilization, the seeds from the Recessive (here 

 dwarf) plants produced only dwarfs, and these were found 

 to breed true from generation to generation. On the 

 other hand, the seeds from the taU or Dominant plants, 

 when sown, again produced both tails and dwarfs, the 

 dwarfs always breeding true to type and the taUs only true 

 in the proportion of 1 to 2. The taUs which breed true 

 are called pure Dominants ; those that do not are hybrids 

 or impure Dominants. 



Thus on sowing the seeds of any generation the result 

 is always : 



Dominants : Recessives : : 3 : 1. 



The Recessives breed true, but only one-third of the 

 Dominants ; so that the real constitution of any generation, 

 only to be ascertained by sowing its seeds, is : 



Pure Dominants : Impure Dominants or Hybrids : Recessives 

 = 1 : 2 : 1 



