in Hybridisation 67 



it in every case confirmed that constant progeny can only 

 be formed when the egg cells and the fertilising pollen are 

 of like character, so that both are provided with the material 

 for creating quite similar individuals, as is the case with the 

 normal fertilisation of pure species*. We must therefore 

 regard it as essential that exactly similar factors are at work 

 also in the production of the constant forms in the hybrid 

 plants. Since the various constant forms are produced in 

 one plant, or even in one flower of a plant, the conclusion 

 appears logical that in the ovaries of the hybrids there are 

 formed as many sorts of egg cells, and in the anthers as 

 many sorts of pollen cells, as there are possible constant 

 combination forms, and that these egg 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 egg and pollen cells were formed in the hybrids on the 

 average in equal numbers f. 



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 t B, a, b, we have : 



AB, seed parent; ab, pollen parent; 



A, form round; a, form angular; 



B, albumen yellow. b, albumen green. 



* [" False hybridism " was of course unknown to Mendel.] 

 t [This and the preceding paragraph contain the essence of the 

 Mendeliau principles of heredity.] 



52 



