250 Emerson. 



could have come about mily if the colorless-seeded plant were either 

 ccrrppil, CCrrppIi or ccUUppIi, in which I represents an inhibiting 

 factor. It can be shown, however, that no inhibitor is concerned here 

 and that, therefore, the first of the three formulae is the correct one. 



The colorless-seeded plant, noted in connection with these formulae, 

 was grown from a self-pollinated seed of a colorless-seeded plant which 

 in turn was grown from a colorless seed of a cross-pollinated ear con- 

 taining 251 purple and 88 colorless seeds, or about three purple seeds 

 to one that was colorless. The plant that bore this cross-pollinated 

 ear produced also a colorless ear by self-pollination and the plant that 

 furnished the pollen had a self-pollinated ear with red and colorless 

 seeds in approximately a 3 — 1 ratio. These results could not have 

 been produced if a factor that inhibits aleurone color had been present 

 even in a heteroz3'gous condition. It can also be shown from these 

 results that some plants lacking all the four factors C, R, P and I 

 were 1o have been expected among the colorless-seeded progeny. 



It follows from all this that the colorless-seeded plant, upon a 

 cross-pollinated ear of which the half-purple, half-red seed was found, 

 must have had the formula ecrrpp. It will be recalled that the pollen 

 concerned in the production of this seed and of the other seeds on the 

 same ear was a mixture of eight sorts, coming from a plant with the 

 formula CcRrPp. 



If the purple-and-red seed was due to a somatic segregation, that 

 seed must have been one that would otherwise have been pui-ple. The 

 endosperm of such a purple seed must have had the formula CccRrrPpp. 

 Any segregation, including all the heterozygous factors and of such a 

 nature that C, R and P went to one daughter cell, would have made 

 it impossible that any of these factors could have gone to the other 

 daughter cell. This would have resulted in a purple-white not a purple- 

 red seed'). If, therefore, the purple-red seed were produced as the result 

 of a segregation at all, only the factor P could have been concerned. 



If the purple-red seed was due to a somatic mutation, it seems 

 likely that the change was from purple to red by the loss or modifi- 

 cation of the P factor. There is, however, the possibility that the 



^) A purple-wliite .seed (figure 7) was t'ouuil, as was also a red-wliite one (figure 8), 

 on this same ear, but it is not necessary to assume that it was produceil tlirough a 

 segregation involving all three factors. If either R or C were alone concerned, the 

 same result must have followed. That three anomalous seeds should have occurred on 

 this one ear, while so many ears have no such seed, is to me unaccountable. 



