STRUCTURE OF THE MAIZE EAR AS INDICATED IN 

 ZEA-EUCHLAENA HYBRIDS 



By G. N. Collins 



Botanist, Office of Acclimaiization and Adaptation of Crop Plants, Bureau of Plant 

 Industry, United States Department of Agriculture 



INTRODUCTION 



In attempting to trace the origin of maize {Zea mays L.) the center of 

 interest is the evolution of the pecuHar form of inflorescence, especially 

 the pistillate inflorescence, or ear. 



Since Euchlaena {Euchlaena mexicana Schrad.) or teosinte, the nearest 

 known relative of maize, has a very different type of pistillate inflorescence, 

 it may be instructive to compare the two genera and trace the successive 

 changes that would be required in passing from the Euchlaena form of 

 pistillate inflorescence to the maize ear. 



Euchlaena and maize cross freely, resulting in intermediate hybrids 

 which in subsequent generations grade back to the parental forms (PI. i6). 

 It is therefore possible to present a complete series of intermediates, gradu- 

 ated to any desired degree of minuteness. It should be kept in mind that 

 although we may be able to arrange a continuous series of forms ranging 

 from Euchlaena to maize, these forms may not represent the course of 

 evolution. A study of these intermediate hybrids may be expected, 

 however, to throw light on the morphology of the ear and to explain its 

 evolution, at least in a mechanical sense. 



DESCRIPTION OF MATERIAL 



The fonns here described as intermediate between maize and Euchlaena 

 appeared for the most part among the descendants of a cross between 

 Florida teosinte and a diminutive variety of popcorn called "Tom 

 Thumb." Of this cross six first-generation plants were grown and from 

 the self -fed seed of one of these a second generation consisting of 127 

 plants was produced. Several hundred third-generation plants from open 

 pollinated seed were also examined. 



Although in general appearance the pistillate inflorescences of maize 

 and Euchlaena are so unlike that comparisons are difficult, the structure 

 of the flowers is practically identical. The chief differences are therefore 

 to be sought in the structure of the inflorescence and the arrangement of 

 the spikelets. 



Journal of Agricultural Research, (127) Vol. XVII, No. 3 



Washington, D. C. June 16, 1919 



rx Key No. 0-175. 



