MENDEL'S LAW 15 



materials for the production of both roundness and 

 wrinkledness. If the materials be represented by their 

 initial letters, with capitals for dominants and small 

 letters for recessives, then the following diagram should 

 represent the distribution of the materials in the 

 hybrids : 



In the ovaries In the anthers 



R R 



w w 



Since the materials in the ovaries unite with those in 

 the anthers and since there are two kinds of materials 

 in both ovaries and anthers, the chances of the four 

 combinations RR, Rw, wR, and ww being formed are 

 equal. A further diagram will make this clearer : 



.R 



.w 



-.— ^R. 

 <:^S» w. 



The combinations Rw and wR being the same, the 

 chances are 1:2:1 that the combinations RR, Rw, and 

 WW should be formed. But, as all the progeny receiving 

 the materials RR and Rw should be round while those 

 receiving the materials ww should be wrinkled, the 

 chances are that three round seeds should be produced 

 for one wrinkled ; and, as the progeny receiving the 

 materials RR should be pure and should breed true 

 while those receiving the materials Rw should be 

 hybrid, the chances are that one only in every three 

 round seeds should breed true. 



Thus expectation is in complete agreement with the 

 results obtained. The hypothesis is consistent with the 

 observed phenomena. 



Consider next the case in which the parents differ in 



