in Hybridisation 357 



anthers as many sorts of pollen cells, as there are possible 

 constant combination forms, and that these ^gg and pollen 

 cells agree in their internal composition with those of the 

 separate forms. 



In point of fact it is possible to demonstrate theoretically 

 that this hypothesis would fully suffice to account for the 

 development of the hybrids in the separate generations, if 

 we might at the same time assume that the various kinds 

 of ^gg and pollen cells were formed in the hybrids on the 

 average in equal numbers'^. 



In order to bring these assumptions to an experimental 

 proof, the following experiments were designed. Two forms 

 which were constantly different in the form of the seed and 

 the colour of the albumen were united by fertilisation. 



If the differentiating characters are again indicated as 

 A, B, a, d, we have : 



AB, seed parent ; ab, pollen parent ; 



A, form round ; a, form wrinkled ; 



B, albumen yellow. b, albumen green. 



The artificially fertilised seeds were sown together with 

 several seeds of both original stocks, and the most vigorous 

 examples were chosen for the reciprocal crossing. There 

 were fertilised : 



1. The hybrids with the pollen oi AB. 



2. The hybrids ,, „ ab. 



3. AB „ ,, the hybrids. 

 ^. ab >, ,, the hybrids. 



For each of these four experiments the whole of the 

 flowers on three plants were fertilised. If the above theory 

 be correct, there must be developed on the hybrids &gg and 

 pollen cells of the forms AB, Ab, aB, ab, and there would 

 be combined : 



T The ^gg cells AB, Ab, aB, ab with the pollen 

 cells AB. 



2. The ^gg cells AB, Ab, aB, ab with the pollen 

 cells ab. 



*■ [This and the preceding paragraph contain the essence of the 

 Mendelian principles of heredity,] 



