134 Journal of Agricultural Research voi. xvii. no. 3 



With the recognition of the fact that the interrupted rows represent 

 pedicelled spikelets instead of the pedicelled and sessile spikelets of a 

 row of alicoles the position of the interrupted rows with respect to one 

 another becomes of importance in studying the formation of the ear. 



Following the fasciation theory, if both of the rows of pedicelled spike- 

 lets of a single branch aborted leaving the sessile, we should find the 

 two interrupted rows separated by two remaining rows. (This may 

 be illustrated by reference to fig. i , D. If the two rows of pedicelled 

 spikelets marked a were aborted the two missing rows would be sepa- 

 rated by two rows.) This is not what occurs. In the examination of 

 many ears in which rows were dropped no instance has been found where 

 the dropped rows were either adjacent or separated by two rows. In 

 cases where the location of the dropped rows can be determined with 

 reasonable certainty the dropped rows are on opposite sides of the ear. 

 Yet they are not exactly opposite, but missing, it by just two rows. This 

 is what should occur if the two pedicelled spikelets were dropped simul- 

 taneously from a pair of yoked alicoles. It will be recalled that the dorso- 

 ventral arrangement of the spikelets in the original four-rowed spike re- 

 sults in bringing the pedicelled spikelets not exactly opposite, but sepa- 

 rated by two more rows on one side than on the other. (See fig. i, E. 

 The pedicelled spikelets of a pair of yoked alicoles are marked a. It 

 will be seen that they are separated on one side by six rows and on the 

 other by eight.) 



The persistence with which ears of maize maintain an even number of 

 rows is therefore more wonderful than has been supposed, for it can not 

 be fully accounted for by the fact that the spikelets are bom in pairs. It 

 must, in addition, be recognized that when a pedicelled spikelet of one 

 alicole is suppressed there is a simultaneous suppression of the pedicelled 

 spikelet in another alicole. The further evidence afforded by Kuchlaena 

 hybrids is that the two alicoles are the members of a yoked pair which 

 though standing on opposite sides of the ear, have not lost their identity 

 as a structural and developmental unit. 



SUMMARY 



Before the pistillate inflorescences of maize and Euchlaena could be 

 compared in detail it was found necessary to recognize as a morphological 

 unit the organs borne by a single metamer of the rachis. This unit, 

 whether staminate or pistillate, whether composed ot one or more 

 spikelets, has been called an alicole. 



The stages between a Euchlaena spike and a maize ear as they appear 

 in hybrids between the two genera may be summarized as follows: 



(i) The suppressed pedicelled spikelet in each alicole reappears. 



(2) The alicoles become more crowded and their -number is increased. 



(3) The alicoles associate themselves in pairs or yokes. (4) The axis 

 twists, increasing the rows of alicoles. 



