[Cir. 124— B] 



EFFECTS OF CROSS-POLLIXATION ON THE SIZE OF SEED IN 



MAIZE/ 



By G. N. Collins, Botanist, and 3. H. Kemptox. Assistant, Office of Crop Acclimati- 

 zation and Adaptation Investigations. 



INTRODUCTION. 



There is a popular belief that the immediate effect of planting two 

 varieties of maize in close proximity is to increase the yield of both 

 varieties. Failure to appreciate some of the pecuhar characteristics 

 of the maize plant accounts for the delay in bringmg this question to 

 the test. With other crops the changes wliich follow crossmg become 

 apparent only when the hybrid embryos develop into plants m the 

 next generation after the crossing takes place. In maize, however, 

 foreign pollen often has an immediate effect in altermg the color and 

 texture of the seeds, a phenomenon that has received a special name, 

 xenia. It seemed, therefore, not unreasonable to believe that the 

 size of the seed as well as the color or texture might be affected by 

 crossing. 



In comiection with a study of hybrids between United States varie- 

 ties and a new type of maize from Chma it was observed that one of 

 the effects of crossing the two types was an increase in the size of the 

 seed in the same year the crossing was done.^ Similar results in 

 crosses of tliis Chinese variety have been recorded by Roberts. ^ 



Additional data on this subject were obtamed in connection with 

 an experiment planned to test the possibihty of selective pollmation 

 in maize. Pollen taken from two plants belongmg to different varie- 

 ties was mixed and applied to the stigmas or silks of one of the varie- 

 ties, thus producmg pure and hybrid seed on the same ear. The 

 phenomenon of xenia made it possible to so select the varieties with 

 respect to color of the seed that it was possible to distinguish between 

 the hybrid seeds and those resulting from the pollen of the same 

 varietv. 



1 Issued May 3, 1913. 



2 CoUins, G. N. A new type of Indian com from Thina. V . S. Department of Agriculture, Bureau of 

 Plant Industry, Bulletin 161, p. IS, 1909. 



Roberts, H. F. First generation hybrids of American X Chinese com. American Breeders' Asso- 

 ciation, Annual Report, v. 7/8, p. 374, 1912. 



89366°— Cir. 124—13 2 - 9 



