June i6, 1919 Structure of Maize Ear 131 



frequent and obvious indications of admixture with maize is a shortening 

 of the rachis. The reduction in length, however, is not uniform but is 

 more pronounced in alternate internodes, with the result that the alicoles 

 become associated and yoked in pairs, the members of which stand nearly 

 opposite to each other. 



In the staminate inflorescence of either Euchla,ena or the common 

 varieties of maize there is little indication of this yoking of the alicoles. 

 The pairs of spikelets stand on opposite sides of the rachis, but usually 

 they are equally spaced with no indication of yoking, this tendency not 

 even appearing in the pistillate inflorescence of the first generation of 

 the hybrid between maize and Euchlaena. Yoking of the alicoles is, 

 however, a striking characteristic of the second generation and appears 

 in all the stages between the four-rowed spike and a well-formed ear. 

 With the increase in the number of ranks of alicoles this yoking of the 

 alicoles into pairs is obscured, but there are evidences that it still persists 

 even in the fully developed many-rowed ear. 



In addition to the sharply contrasted characters discussed above, the 

 pistillate inflorescence of maize differs from that of Euchlaena in having 

 the alicoles much more numerous and more closely crowded. 



EUCHLAENA X MAIZE HYBRIDS 



Having outlined the nature of the differences between the pistillate 

 inflorescences of Zea and Euchlaena, the pistillate inflorescences of the 

 hybrid plants may now be examined. In the first generation the spike- 

 lets are paired, the alicoles separate, and two-ranked. In number of 

 alicoles and degree of crowding they are intermediate between the 

 parents. This mixture of characters derived from both parents creates 

 the general impression that the inflorescence is intermediate. 



SECOND AND LATER GENERATIONS 



Treating the three contrasted characters of maize and Euchlaena as 

 alternative, there are eight possible combinations: (i) Spikelets single, 

 alicoles separate and two-ranked; (2) spikelets single, alicoles separate 

 and many-ranked; (3) spikelets single, alicoles }^oked and two-ranked; 

 (4) spikelets single, alicoles yoked and many- ranked; (5) spikelets paired, 

 alicoles separate and two-ranked; (6) spikelets paired, alicoles separate 

 and many-ranked; (7) spikelets paired, alicoles yoked and two-ranked; 

 and (8) spikelets paired, alicoles yoked and many-ranked. With the ex- 

 ception of No. 6, all of these combinations have been found in second- 

 generation plants and most of them in the descendants of a single cross. 

 To class the individuals into the above eight combinations is, however, a 

 very inadequate expression of the diversity. The dominance shown in 

 the first generation was not followed by any clear-cut segregation in the 

 second. On the contrary, a complete series of intermediates connected 

 the parental forms with respect to each of the three contrasted pairs of 

 characters. 



