CHARACTERS OF DISTINCT PAIRS iii 



" purple spot " simply. A specimen is shown in 

 Fig. 26. 



When peas bearing these two varieties of seed-coat 

 are crossed, there results a hybrid, the seed- coat of 

 which exhibits both the " maple " and the " purple 

 spot " character, which is seen below and between 

 the two parent forms in Fig. 26. This result is 

 rather surprising, because it might have been supposed 

 that " maple " and " purple spot " were the dominant 

 and recessive members of a single pair of characters 

 from the fact that they were stated to characterise 

 one and the same part of the plant, namely, the seed- 

 coat. It will be remembered that one feature of 

 characters which constituted a Mendelian pair of 

 characters was said to be the fact that they pertained 

 to the same part of the organisation of the animal 

 or plant which bore them ; and it might be supposed 

 that the converse was true, namely, that two 

 characters which pertained to a particular part of 

 the plant, if so facto, constituted a pair of Mendelian 

 characters. But the fact that both " maple " and 

 " purple spot " are simultaneously present in the 

 hybrid shows that these two characters do not con- 

 stitute a pair, but are members of distinct pairs. 

 The generalisation, however, in regard to the common 

 location of the two members of a pair of characters, 

 and the converse of this generalisation are saved by 

 the fact that there are two layers in the seed- coat 

 of the pea, an outer and an inner, and that the 

 pigment to which the " mapling " is due is 

 lodged in one of them and the pigment which 



