V 



188 MAIZE 



CHAP, in the F 3 generation, they are usually considered pure {East 

 and Hayes, i ), but if the absence of yellow is due to the absence 

 of a factor on which the appearance of colour depends, they 

 may, even though heterozygous, continue to breed white until 

 crossed with another white carrying the complementary factor, 

 when yellow will appear. The relative amount of soft and 

 horny starch contained in the seed is one cause of varying in- 

 tensity of the yellow colour in F 2 crosses between yellow and 

 white. 



East and Hayes appear to have found six shades of yellow 

 in the progeny of a cross between yellow and white maize, for 

 they observe that " in the case of the two yellow colours in 

 the maize endosperm, the intensity of the yellow decreases in 

 the following order : — 



V, Y, Y, Y 2 



Y, y, Y, Y 3 or Y, Y, Y, y 2 



Y 1 Y 1 or Y, Y, 



\\ y, or Y, y„ 



>'i Yi Ya Y2 [i- e * pure white ?] " 



The present writer has found six shades of yellow in the 

 F., seed generation, and ten shades in the F, seed generation 

 after crossing with white. The two yellows already referred 

 to are involved in the production of these shades, and there 

 is a distinct break in the gamut of tints between what appears 

 to be the palest of No. I, and the darkest of No. 2. 



142. " White Starchy" Endosperm. — This was shown to be 

 a Mendelian dominant by Correns in 1 90 1, and confirmed by 

 Lock in 1904, and later by the writer and by East and Hayes 

 working simultaneously though unknown to each other. East 

 and Hayes found that dominance was complete ; in no case 

 was there the slightest difference between the homozygous and 

 the heterozygous seeds in either outward appearance or in the 

 character of the starch cells when examined microscopically. 



143. Inheritance of Characters which Affect the Growing 

 Plant. — The characters which we have been discussing are those 

 which affect the endosperm, and are therefore visible in the 

 daughter seeds of the ear that has been crossed, i.e. the first 

 new generation. There are other characters, however, affecting 

 the growing plant, which do not show in the seed. These will 

 be discussed seriatim. 



