April 1, 1920 



A Teosinte-Maize Hybrid 



21 



The five tassel characters form a closely correlated group. With few 

 exceptions all the members of the group show similar relations with 

 other characters. With the exception of secondary index, all are direct 

 measurements that might be expected to increase with increased vigor; 

 and were it not for this character the correlations with the direct measure- 

 ments in the height group might be considered physiological. The same 

 may be said of the nodes above group. The disherent correlation of 

 tassel branches on third with nodes on third branch is also physiological, 

 since a highly developed third branch would naturally have a larger 

 number of tassel branches. 



The clearest evidences of coherence are the correlations of secondary 

 index with rows in central spike and that between secondary branches 

 and branch silking first. Disherence is indicated by the negative correla- 

 tions between all the tassel characters and the two 



characters male secondaries and length of internode on 

 third. 



MALK BRANCH GROUP 



MALE BRANCH INDEX 



P 



30 



\^ 





^W^ 



4ff 



This character Vv-as calculated by dividing the num- 

 ber of branches terminating in staminate inflorescences, 

 excluding suckers, by the total number of leaves and 

 multiplying by 100. It is thus the number of male 

 branches expressed as a percentage of total leaves or 

 internodes of the main culm. 



In normal maize none of the branches above the 

 suckers bear staminate flowers, although staminate tips 

 and perfect flowered spikelets are common abnormal- 

 ities. In teosinte all primary branches normally end 

 in a staminate inflorescence. There is, then, no over- 

 lapping of either of the varieties or species with respect 

 to this character. 



The F2 hybrid plants ranged from o to 71 with the 

 mean at 37. The distribution (fig. 14) is practically 

 symmetrical and clearly unimodal. 



There are four significant correlations, all in the direc- 

 tion of coherences. They are with nodes without branches, nodes above, 

 alicole index, and branch silking first. Except in the correlation with 

 alicole index, a physiological explanation is suggested. 



MALE SECONDARIES 



As a measure of this character, all secondary branches on the third 

 branch from the top of the plant that bore staminate spikelets were 

 counted. 



Fig. 14. — Male branch 

 index: frequency dis- 

 tribution of plants in 

 F2. Class value, lo 

 per cent. 



