228 HISTORY OF BOTANY 



intermediates appearing. Obviously, tallness was a 

 character that overpowered dwarfness, so to speak, so 

 he termed the character tallness " dominant " and 

 dwarfness " recessive." He then cultivated the seeds 

 resulting from the self -fertilisation of all these tall hybrids, 

 but, instead of obtaining a second generation of tall plants, 

 he got a mixture of tall and dwarf, again without any 

 intermediates. After a number of experiments he 

 discovered a remarkable numerical relation between the 

 tall and the dwarf plants, viz. the former were found 

 to be on the average three times as numerous as the 

 latter. 



The next step was to self-fertilise all the offspring of 

 the hybrids of the second generation and collect and 

 grow their seed in turn. The result was again unexpected. 

 The seeds of the dwarf plants developed into dwarf plants 

 and continued to breed true dwarfs in subsequent genera- 

 tions. Further, one-third of the tall plants also continued 

 to breed true. The seeds from the remainder of the tall 

 plants, however, behaved exactly in the same way as 

 the tall plants of the first generation when self-fertilised, 

 i.e. three were tall to every one dwarf. Expressed 

 numerically, in the second generation out of every 

 hundred plants 75 were tall and 25 were dwarf, and 

 out of the 75 tall forms 25 bred true, so that as a final 

 result we have 25 tall breeding true, 25 dwarf breeding 

 true, and 50 tall not all breeding true but prepared to 

 breed in the same proportion as the original first genera- 

 tions of hybrids. 



The results of Mendel's experiments have been 

 summarised by Professor Punnett in the following words : 

 " In every case where the inheritance of an alternative 

 pair of characters was concerned the effect of the cross 

 in successive generations was to produce three and only 

 three different sorts of individuals, viz. dominants 

 which bred true, dominants which gave both dominant 

 and recessive offspring in the ratio of three to one, and 



