SELECTIVE FERTILIZATION IN POLLEN MIXTURES. 263 



source than 126, and somewhat different in type, self-fertilized 

 two years. 



Mixtures number i to 9 inclusive comprise various inbred 

 strains with yellow starchy and white starchy endosperm. Some 

 of these strains have been described previously (Jones, 1918) and 

 all show marked heterosis in the crossed seeds and in the resulting 

 first generation hybrid plants. A sample of all the different lots 

 of seed secured in these mixtures have been grown to test the 

 accuracy of classification. Pollen mixtures number 10 to 12 

 are not from inbred strains but from first generation hybrids, one 

 having all yellow seeds the other all white. They were of such 

 a constitution that the second crossing gave still more increase 

 in vigor although not as great as the stimulus following the 

 first cross. The plants being vigorous a large amount of seed 

 was obtained from a few plants. It was desired to know whether 

 the same selective action would be shown by vigorous plants 

 with segregating gametes as contrasted with non-vigorous plants 

 whose gametes were all alike. Classification of the seed was 

 easily carried out and the per cent, of error when tested was 

 found to be quite low. Mixtures 13 and 14 involved yellow 

 sweet in one strain and white starchy endosperm in the other. 

 One dominant factor was carried by each so that differentiation 

 was perfectly distinct in the reciprocal applications. In mixtures 

 15 and 16 it was intended to make use of the same characters 

 as in the two preceding numbers. The plants which were sup- 

 posed to be inbred individuals of a yellow sweet strain, and so 

 labeled, when grown in the field were seen to be too vigorous for 

 this material as it had behaved in previous years. The plants 

 were all alike, however, in this respect. It was suspected that 

 this was a lot of first generation hybrids instead of plants from 

 self-fertilized seed. As some crosses had been made with plants 

 of this line the previous season it is now certain that in this 

 instance the seed was not properly labeled at harvest and so was 

 planted for self-fertilized seed when in reality it was all cross- 

 fertilized. As no other plants were available at the time they 

 were needed these were used. Several self-pollinations were 

 made at the same time to show what the seed characters were of 

 this undoubted hybrid. At maturity it definitely showed itself 



