MOSAIC COHERENCE OF CHARACTERS IN SEEDS OF MAIZE, 21 



by a colored aleurone. In the second example, the waxy parent was 

 white and in the mosaic seed from this cross the waxy portion of the 

 seed is white. In both seeds the form of the colored spot is irregvdar 

 and the line separating the two kinds of endosperm follows the irregular 

 margin of the spot with great precision. 



In the second example, Dh209, the tendency for the white and waxy 

 characters to be associated is also shown in the usual way by the rela- 

 tive numbers of seeds in the different classes. The ear had 561 seeds. 

 Aside from the mosaic seeds these were readily separated into six 

 perfectly distinct classes, as follows: Colored horny, 295; white 

 horny, 42; colored sweet, 101; white sweet, 34; colored waxy, 35; 

 white waxy, 53. Considermg the entire ear, 23 per cent of the seeds 

 are white, but of the 88 waxy seeds 60.2 per cent are white. 



It miirht be urged that the correlation sho^Am m the mosaic seeds is 

 physiological. There may be some physiological or chemical reason 

 why a colored aleurone conduces to the development of a waxy tex- 

 ture in the endosperm immediately beneath it, or the waxy endosjjerm 

 might react on the aleurone immediately above it in a way to produce 

 color. But the fact that the coherence is between colored aleurone 

 and waxy endosperm in one example and between colored aleurone 

 and horny endosperm in the other renders any strictly chemical expla- 

 nation inadequate. 



The JSlendelian conception of coherence or gametic coupling is that 

 attractions or repulsions exist between character determinants, 

 causbig certain combinations in the gametes to occur more frequently 

 than others. This explanation can not be applied to examples of 

 mosaic coherence, smce in the case that represents the first-generation 

 hybrid (Dh359) the segregation has not yet taken place. If we are 

 to venture into this dangerous field of speculation it seems more 

 reasonable to think of the parental gametes as being imperfectly 

 combined, the two parts of the seed falling under the influence of 

 different parents. 



Whatever may prove to be the cytological explanation, these 

 mosaic seeds make the phenomenon of coherence appear more tangible 

 and direct by affordmg a visible exami)le. 



[Cir. 132] 



o 



