MENDEL'S WORK 



19 



exclusive so far as the gamete was concerned. It 

 must be pure for one or the other of such a pair, 

 and this conception of the purity of the gametes is 

 the most essential part of Mendel's theory. 



We may now proceed with the help 

 accompanying scheme (Fig. i) to deduce 

 suits that should 



Tall ^ /.-^ 



Parent ^B (J- - 



gametes ^ ^ O O gametes 



of 

 the 



the 

 re- 



^' 



flow from Mendel's 

 conception of the 

 nature of the gam- 

 etes, and to see 

 how far they are 

 in accordance with 

 the facts. Since 

 the original tall 

 plant belonged to 

 a strain which bred 

 true, all the gam- 

 etes produced by it 

 must bear the tall 

 character. Simi- 

 larly all the gam- 

 etes of the original 

 dwarf plant must 

 bear, the dwarf character. A 

 two means the union of 

 tallness with one bearing 

 to the completely dominant 

 character, such a plant is in 

 tinguishable from the pure 



Dwarf 

 -Parent 



• - 



generation 



Fig. 1. 



Scheme of inheritance in the cross of tall with dwarf 

 pea. Gametes represented by small and zygotes 

 by larger circles. 



a 



a 



lo- 



-Os 

 e 



-9 bo 



-OS 



cross between these 

 a gamete 



containing 



dwarfness. Owing 



nature of the tall 



appearance indis- 



tall, but it differs 



markedly from it in the nature of the gametes to 

 which it gives rise. When the formation of the 

 gametes occurs, the elements representing dwarfness 



