SELECTIVE FERTILIZATION IN POLLEN MIXTURES. 267 



is dependent upon the numbers in the less populous half of the 

 proportion. 



Some of the mixtures have over one thousand individuals in 

 each of the four classes. Since the experimental error is low 

 and not all in one direction as has been shown and the selective 

 elimination of zygotes tends to obscure the result which has 

 been obtained, such figures as these can not be gainsayed. Of 

 the 20 mixed pollinations 17 show a deviation indicating a 

 selective action in favor of the plants' own pollen. While three 

 of the mixtures show the opposite effect. These three are all 

 low in number of individuals on one or the other side of the pro- 

 portion. Mixtures 6 and 7 could not be classified by the seeds on 

 the yellow seeded plants so consequently the progenies were 

 grown and classified at maturity. This brings in other sources 

 of error differential germination and competition between plants 

 which are weak with those that are vigorous which certainly 

 tend to result to the apparent advantage of cross-fertilization. 

 Two of the deviations showing an excess of self-fertilized indi- 

 viduals are not significant when compared to the allowable 

 differences from random sampling but all the others are. There- 

 fore the conclusion is inevasible that in maize the plant's own 

 pollen is more effective in consummating fertilization than pollen 

 from plants of only slightly different construction. This selec- 

 tive action is shown even though the foreign pollen is perfectly 

 capable of fertilizing the plants when not acting in competition 

 with the plant's own kind of pollen as has been definitely proven. 

 Mixtures number 15, 16 and 17 show 47 out of a possible 50 

 per cent, deviation, almost complete non-functioning of the 

 unfamiliar pollen. Numbers 15 and 16 include the first genera- 

 tion hybrids in which some calculations had to be made to allow 

 for segregation but these are perfectly justifiable adjustments 

 and the results can be discounted but very little. Mixture 17 

 is low in numbers having only 104 seeds on the B plants of which 

 4 are cross-fertilized. But observe the result when this same 

 mixture is applied to the A plants. Here only 3 cross-fertilized 

 seeds are to be found among 1,303 self-fertilized seeds. Surely 

 there is some powerful action working to hold back the unfamiliar 

 pollen. Mixtures number 3, 4, 8, 10, 19 and 20 are by them- 



