360 Mendel's Experiments 



draws attention, viz. that " it depends which individual is 

 chosen for further transformation." Experiments which in 

 this connection were carried out with two species of Pisum 

 demonstrated that as regards the choice of the fittest 

 individuals for the purpose of further fertilisation it may 

 make a great difference which of two species is transformed 

 into the other. The two experimental plants differed in 

 five characters, while at the same time those of species A 

 were all dominant and those of species B all recessive. 

 For mutual transformation A was fertilised with pollen of 

 B, and B with pollen of A, and this was repeated with 

 both hybrids the following year. With the first experiment 



T) 



--T there were eighty-seven plants available in the third 

 A. 



year of experiment for selection of the individuals for 



further crossing, and these were of the possible thirty-two 



^ 

 forms ; with the second experiment -~ seventy-three plants 



resulted, which agreed throughout perfectly in habit with 

 the pollen parent ; in their internal composition, however, 

 they must have been just as varied as the forms in the 

 other experiment. A definite selection was consequently 

 only possible with the first experiment ; with the second 

 the selection had to be made at random, merely. Of the 

 latter only a portion of the flowers were crossed with 

 the A pollen, the others were left to fertilise themselves. 

 Among each five plants which were selected in both 

 experiments for fertilisation there agreed, as the following 

 year's culture showed, with the pollen parent : 



ist Experiment 2nd Experiment 



2 plants in all characters 



3 11 4 



2 plants 3 



2 2 ,, 



i plant ,, i character 



In the first experiment, therefore, the transformation 

 was completed ; in the second, which was not continued 

 further, two more fertilisations would probably have been 

 required. 



Although the case may not frequently occur in which 



