408 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1937 



astounding, and each year finds more mutations awaiting analysis. 



The heritable units thus far studied affect all parts of the organism 

 ranging from genes that exhibit their reactions only in the pollen 

 grains, through seed and seedling characters, to those that alter the 

 entire plant. There are genes that change all the female flowers to 

 males (pi. 30, fig. 2), others that reverse this process to the same end 

 and change all male flowers to females. Others undo the separation 

 of the sexes and make the plant perfect-flowered. 



These changes, interesting from the standpoint of heredity, are 

 also of interest in view of the uncertain antecedents of corn. The 

 possession of numerous genes that profoundly modify sex expression 

 suggests that maize may have, not far back in its descent, a perfect- 

 flowered ancestor. From existing knowledge of inheritance it has 

 been possible to create true breeding strains having male and female 

 plants in equal numbers and capable of self-perpetuation. It is also 

 possible to develop a perfect-flowered form of maize with the seeds 

 borne on the familiar tassel instead of on an ear and which, if com- 

 bined with some of the genes for dwarf stalks, would produce a crop 

 that could be harvested with a combine just as is wheat or the dwarf 

 forms of grain sorghum. 



The possibiUty of improving upon our heritage from the Indians 

 is very real and is commanding the attention of an active group. 

 Even now, through the stimulation derived from a purely theoretical 

 extension of our knowledge of inheritance, hybrids far surpassing the 

 best varieties have been obtained and a system de\'ised for their com- 

 mercial use. That the future holds even greater things for corn with 

 the increase in knowledge of gene interaction is a certainty. 



