130 Journal of Agricultural Research voi. xvri. No. 3 



TWO-RANKED AND MANY-RANKED ALICOLES 



The manner by which the number of rows has been increased iu the 

 pistillate inflorescence of maize has been the subject of much contro- 

 versy. Two ways of developing additional rows have been suggested — 

 by fasciation of long lateral branches of a compound inflorescence like 

 the tassel/ or by the reduction of branches until each branch is repre- 

 sented by a single pair of spikelets. 



The fasciation theory v/ould explain the ear and the central spike 

 of the tassel in the same way, by assuming that a many-rowed spike has 

 resulted from the fusion of simple spikes or branches. In the terminal 

 inflorescence of pure Euchlaena there is no indication of a central spike, 

 all the branches being similar, except that the lower are again subdi- 

 vided. If two of the upper branches of such an inflorescence were to 

 coalesce, an eight-rowed spike would be formed, and if then the pedicelled 

 spikelets should become sessile and all the spikelets pistillate, an eight- 

 rowed ear would result. 



According to the second or reduction hypothesis the development of 

 the ear and the central spike of the staminate inflorescence is supposed 

 to have been accomplished through a shortening of the branches in the 

 upper part of an inflorescence similar to the staminate inflorescence of 

 Euchlaena, the branches being reduced until each was represented by a 

 single pair of spikelets. In apparent conflict with this view is the abrupt 

 transition between the uppermost branch and the lowest spikelets of the 

 central spike, that characterizes all normal varieties of maize. But in 

 the mutation known as Zea ramosa the abrupt transition is lost, so that 

 the branches become gradually shorter and pass by imperceptible grada- 

 tion into simple pairs of spikelets like those of a normal tassel. Thus, 

 Z. ramosa may be looked upon as representing an intermediate stage 

 in the formation of a central spike, and as such constitutes the chief 

 support of the reduction theory. 



The evidence derived from hybrids of maize and Euchlaena does not 

 support either of these theories. On the contrary, the hybrid plants pro- 

 vide an unbroken series of stages connecting the Euchlaena spike with the 

 maize ear that clearly indicates a third method of increasing the number 

 of rows and forming a central spike or ear. This is by shortening and 

 twisting the rachis of a single spike of Euchlaena, accompanied by an 

 increase in the number of alicoles. The stages in this process will be 

 discussed in more detail later. 



SEPARATE AND YOKED ALICOLES 



In the pistillate inflorescence of pure Euchlaena the joints of the 

 rachis, each of which bears a single alicole, stand almost directly above 

 one another, resembling a string of triangular beads. One of the most 



' The earliest published statement of the fasciation theory that has thus far come to light is an anonymous 

 account (Sexual flowers in Indian corn), in Meehan's Monthly, v. 3, p. 105, 1S93. 



