MENDEL 



periments, the results of which appear 

 fitted to afford some conclusions as 

 regards the composition of the egg and 

 pollen cells of hybrids. An important 

 clue is afforded in Pisimi by the cir- 

 cumstance that among the progeny of 

 the hybrids constant forms appear, and 

 that this occurs, too, in respect of all 

 combinations of the associated char- 

 acters. So far as experience goes, we 

 find 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 certain that exactly similar 

 factors must be at work also in the 

 production of the constant forms in 

 the hybrid plants. Since the various 

 constant forms are produced in ojie 

 plant, or even in ojie 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 dem- 

 onstrate theoretically that this hypo- 

 thesis 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 vari- 

 ous kinds of egg 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 follow- 

 ing experiments were designed. Two 

 forms which were constantly different 



17 [This and the preceding paragraph con- 

 tain the essence of the A'lendelian principles 

 of heredity.] 



15 



in the form of the seed and the colour 

 of the albumen were united by ferti- 

 lisation. 



If the differentiating characters are 

 again indicated as A, B, a, b, we have: 



AB, seed parent; 



A, form round; 



B, albumen yellow. 

 ab, pollen parent; 



a, form wrinkled; 



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 ferti- 

 lised: 



1. The hybrids with the pollen of 



AB 



2. The hybrids with the pollen of 

 ab. 



3. AB with the pollen of the hy- 

 brids. 



4. ab with the pollen of 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 de- 

 veloped on the hybrids egg and pollen 

 cells of the forms AB, Ab, aB, ab, and 

 there would be combined: 



1. The egg cells AB, Ab, aB, ab with 

 the pollen cells AB. 



2. The egg cells AB, Ab, aB, ab with 

 the pollen cells ab. 



3. The egg cells AB with the pollen 

 cells AB, Ab, aB, ab. 



4. The egg cells ab with the pollen 

 cells AB, Ab, aB, ab. 



From each of these experiments 

 there could then result only the fol- 

 lowing forms: 



