Ill 



MENDEL'S WORK 



19 



Tall 

 Parent 



gametes 



Dwarf 

 Parent 



\ 



D. 



o 



(A 



lU 

 ■1-1 

 (U 



a 



a 



e 



— >■ 



->- 



<- - 



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 of the 

 accompanying scheme (Fig. i) to deduce the re- 

 sults that should 

 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 cross between these 

 two means the union of a gamete containing 

 tallness with one bearing dwarfiiess. Owing 

 to the completely dominant nature of the tall 

 character, such a plant is in appearance indis- 

 tinguishable from the pure tall, ,but it differs 

 markedly from it in the nature of the gametes to 

 which it eives rise. When the fcirmation of the 

 gametes occurs, the elements representing dwarfness 



0-- 



o— 



->- 



€ 



■< — 



o 



OM 



<u 

 H 



V 



generation 



Fig. I. 



Scheme of inheritance in the coss of tall with dwarf 



Eea. Gametes represented by small and zygotes 

 y larger circles. 



