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THE AMERICAN NATURALIST [Vol. XLVIH 



yield about one red to two variegated to one white if self- 

 pollinated and one red to one variegated to two white if 

 crossed by white. (This is on the assumption that no S 

 factors are carried by the male gametes.) Let us assume 

 that by lumping together all the seeds listed in the fore- 

 going records as "more than one half red" and as "less 

 than one half red" the whole lot would average about one 

 half red, and compare the results with the expectation as 

 noted above. From grains of these two classes from 

 homozygous ears both selfed and crossed by white, there 

 resulted 19 red-eared and 82 variegated-eared plants, or 

 a ratio of about 1 : 4.3 instead of 1:3. From heterozy- 

 gous ears self-pollinated grains of these two classes 

 yielded 54 red-eared, 85 variegated-eared, and 52 white- 

 eared plants, and similar grains crossed by white yielded 

 7 red-eared, 7 variegated-eared, and 20 white-eared plants, 

 or ratios of 1.04:1.63:1 and 1:1:2.86 instead of 1:2:1 

 and 1:1:2, respectively. The observed ratios are cer- 

 tainly suggestive but must not be given undue importance, 

 for there is no assurance that the seeds used really aver- 

 aged one half red and no assurance that some of the male 

 gametes in the case of the selfed seeds did not carry S. 



We must now examine the results secured in genera- 

 tions later than F 17 and note whether the hypothesis under 

 consideration applies equally well to them. 



It will be recalled that F x red-eared plants that arose 

 from homozygous, variegated ears which had been self- 

 pollinated (see page 99) yielded in F 2 only red-eared and 

 variegated- eared progeny. On our assumption the for- 

 mula of the parent variegated ears was VV, but the red 

 grains of these ears were VS and the gametes associated 

 with them therefore either V or S or all 8. Female 

 gametes carrying 8 would have produced red ears in F x 

 whether the male gametes carried S or V, and female 

 gametes with V could not have produced red ears except 

 when the male gametes uniting with them carried 8. The 

 F l red-eared plants must therefore have been VS or SS, 

 the former being expected much more frequently than the 



