in 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 of the 

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

 sults that should 



flow from Mendel's Parent ^^ (~^ Parent 



conception of the g^^etes^"^ q"^ gametes 



nature of the gam- \ / 



etes, and to see ^m\ 



how far they are ,'^y-^ ^ ' 



in accordance with j-'' ^^ik. 



the facts. Since i^ • j- ^^ -; #fc 



the original tall S _^^ ° 



plant belonged to | •""""^ C/ ^"7"0| 



a strain which bred S q ^ C% '^ 9^ 



true, all the gam- | s 



etes produced by it iS O ^ (^ ■< OS 



must bear the tail genSition 



character. Simi- 



11 11 t- Fig. ±. 



^ o Scheme of inheritance in the cross of tall with dwarf 



etes of the Oricrinal P^^* Gametes represented by small and zygotes 



^ by larger circles. 



dwarf plant must 



bear the dwarf character. A cross between these 

 two means the union of a gamete containing 

 tallness with one bearing dwarfness. Owing 

 to the completely dominant nature of the tall 

 character, such a plant is in appearance indis- 

 tinguishable from the pure tall, but it diiifers 

 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 



