4 BULLETIN 971, U. S. DEPARTMENT OF AGRICULTURE. 



Number of rows of spikelets on the terminal spike of the ear : This char- 

 acter corresponds to the number of rows on a normal ear, but on many ramose 

 ears the terminal spike is so short and irregular that the number of rows can 

 not be definitely determined. 



Length of the terminal spike: The length in centimeters of the unbranched 

 portion of the ear. This measurement corresponds to the length of the central 

 spike of the tassel. 



Terminal spike index : The length of the terminal spike as a percentage of 

 the total length of the pistillate inflorescence. 



Length of the entire ear : The length of the pistillate inflorescence in centi- 

 meters, including the branched and unbranched sections. 



FIRST GENERATION. 



The ramose characteristics of both pistillate and staminate in- 

 florescences entirely disappeared in the first generation. This was 

 in accordance with the results of other investigators as well as the 

 previous experience of the writer. 



Measurements of the several tassel dimensions, however, disclosed 

 the fact that while the normal type of tassel, as represented by the 

 Gordo variety, dominated the conical tassel of the Ramosa parent, 

 nevertheless the Gordo type had undergone alteration, approaching 

 more nearly the dimensions of the common maize tassel. 



The vigor of the first generation was manifested in the size of the 

 tassel, and the measurements of the several parts reflect this vigor. 

 Thus, the length of the entire inflorescence exceeds that of the larger 

 parent, and a subdivision of the inflorescence into the central spike 

 and branching space shows that both of these parts have increased 

 in length. This general increase in size prevents a direct comparison 

 between the tassel dimensions of the F^ and those of the parents, 

 since the factor of heterosis can not be evaluated accurately. It 

 would seem, however, that the length of the branching space, although 

 less than the parental average, has been increased over that of the 

 Gordo parent by a greater percentage than has the length of the 

 central spike. This indicates the influence of the Ramosa parent, 

 which would be expected to increase the length of the branching 

 space at the expense of the length of the central spike. 



A more direct measure of this effect is to be found in the central 

 spike index. The index clearly shows that the proportion of rachis 

 devoted to the production of branches has increased at the expense 

 of the central spike, although the tassel is still of the normal type, 

 the deviation toward the Eamosa parent being apparent only in the 

 measurements. The measurements are given in Table I, and the fre- 

 quency distribution of the central spike index are shown graphically 

 in figure 1. 



