Journal of Agricultural Research 



Vol. XIX, No. I 



NODES ON THIRD 



eo 



n<5/ 



47 





30 



This character is instructive chiefly as a means of throwing light on the 

 homologies between the branches of teosinte and maize and as a means of 

 calculating the average length of internodes on the third 

 branch described below. 



If each husk on an ear of maize represents a node, the 

 third branch from the top, which would still be earlike, 

 would have even in Tom Thumb from 6 to 8 nodes. 

 In other varieties this number would be even larger. 

 On the other hand, if the leaves from which the husks 

 are derived have been subdivided, thus increasing the 

 apparent number of nodes, the number of nodes on 

 this branch of the hybrids might be expected to agree 

 pretty closely with the number in teosinte, which varies 

 from 2 to 5- The modal number in the Fg hybrid plants 

 was 6, the mean was 7.15 , with a range from 4 to 14. 

 There was no indication of bimodality (fig. 9). There 

 k 2c \ I ! -1 ^^^^ ^° indication in the hybrid plants that leaves were 

 subdivided, each leaf being borne 

 on a well-defined internode. The 

 increased number of nodes over 

 that of teosinte goes to support the 

 idea that each of the husks on an 

 ear of maize represents an internode 

 of the branch. 



In common with the other charac- 

 ters of this group, the correlations 

 with secondary branches and pro- 

 phyllary spikes would seem signifi- 

 cant coherences. In these correla- 

 tions a high value of one character 

 is correlated with a low value of 

 the other, and any general tendency 

 to vigor would reduce the correlation. 



The correlations with position of best spike and 

 node silking first are of doubtful significance, there 

 being an obvious physiological connection between 

 these characters and the number of nodes in the third branch. 



All the significant disherent correlations are of a nature that suggests 

 a physiological explanation. 



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 OFfl/OOES- 



Fig. 8. — Nodes above 

 on third : frequency 

 distribution of 

 plants in F2. Class 

 value, one node. 



30 



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 ft 



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Fig. 9.— Nodes on third: 

 frequency distribution of 

 plants in F2. Class value, 

 one node. 



