200 Albinism in Maize 



It seems that the factor " B" dififers from the factor "A" in that it 

 alone can bring about the changes necessary for the production of a 

 distinctly yellowish colour which later becomes slightly greenish, and 

 in some instances develo2)s into full green. 



Continuing the hypothesis that the gametes arising from hetero- 

 zygous green plants of the category in which pure white plants occur 

 may be represented by AB and Ab, and the gametes arising from 

 heterozygous green plants of the category in which yellowish-white 

 plants occur may be represented by AB and aB, then by crossing the 

 two heterozygous green plants one would expect to obtain in Fi four 

 sorts of green plants in approximately equal numbers. The formulae 

 of the resulting F^ plants would be : 



A ABB, 



AABb, 



AaBB, 



AaBh. 

 By growing the second generation it can be shown experimentally 

 whether or not the first generation plants are of the four sorts enu- 

 merated in the foregoing. According to the hypothesis one of every 

 four Fi plants has the formula AABB, and in succeeding generations 

 should breed true gi-een. One of every four has the formula AABb, 

 and, this being identical with one parent, it should yield a progeny of 

 green plants and pure white ones in the ratio of three gi-een to one 

 white. One of every four has the formula AuBB, and as this one is 

 identical with the other parent the succeeding generation should consist 

 of gi-een plants and yellowish-white ones in the three-to-one ratio. One 

 plant of every four has the formula AaBb, and since this one is hetero- 

 zygous for both factors it would be expected to give a second generation 

 consisting of gxeen plants, yellowish-white plants, and pure white plants 

 in the dihybrid ratio of 9 : 3 : 4. In Table II are shown the hypothetical 

 formulae of the plants in the respective classes predicted in F^, together 

 with the expected behaviour in the third generation. 



In order to make the experimental test, self-pollinated ears were 

 secured from eleven F^ plants which were gi'own in the gi-eenhouse. 

 The second generation results are shown in Table III. 



It will be noted that the actual experimental results are very closely 

 in accord with the theoretical expectation fn)m the two-factor hypothesis. 

 That the F^ plants were of ft)ur distinct sorts, as regards the factors 

 concerned in formation of leaf colour, is shown by the respective F^ 



