14 



Journal of Agricultural Research 



Vol. XIX, No. I 



HEIGHT OK SUCKER 



Measurements were taken from the ground to the tip of the tassel of 

 the tallest sucker or tiller and recorded in decimeters. Tom Thumb almost 

 never produces a sucker. In Florida teosinte there are usually numerous 

 suckers of practically the same height as the 

 main culm. The parent varieties are thus 

 widely separated, but there are varieties of 

 maize with suckers taller than any recorded 

 in teosinte. The mean of the F2 hybrid plants 

 was 16.2, ranging from 6 to 27, mth a 

 practically normal distribution (fig. 3). 



The only character outside the group showing 

 a Significant correlation with height of sucker 

 is secondary branches. The correlation is in 

 the direction of a coherence. 



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SUCKER INDEX 



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Pig. 3, — Height of sucker: fre- 

 quency distribution of 

 plants in Fa. Class value, 

 2 drm. 



30 





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This character was determined by dividing 

 the height of the tallest sucker by the height 

 of the plant and multiplying by 100. It is thus 

 the height of the tall- 

 est sucker expressed 

 as a percentage of the 

 height of the main 

 culm. This measurement was taken as the 

 best single expression of the tendency to pro- 

 duce tall suckers. Since Tom Thumb almost 

 never produces suckers, the index is practically 

 zero for the male parent of the hybrid. In 

 Florida teosinte the index is usually about 100. 

 In one population of 87, the mean was 99.4, 

 with a range from 90 to no. In the Fj 

 hybrid plants the mean was 117, with a 

 range from 50 to 460. The distribution (fig. 4) 

 was unimodal and symmetrical with the ex- 

 ception of a few stragglers probably represent- 

 ing plants with abnormal main culms. 



The coherences outside the group are with. 

 male secondaries, mixed alicoles, and length 

 of intemode on third. The disherences are with three members of the 

 height group, nodes on third branch, two of the tassel measurements, 

 position of best spike, branch silking first, and days to pollen. 



There is thus more direct evidence of disherence than of coherence with 

 this character. It should be remembered, however, that the negative 

 correlation of sucker index with height is in a sense physical, since the 



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Fig. 4. — Suckerindex: frequency 

 distribution of plants in F2. 

 Class value, 10 per cent. One 

 plant at 230 and one at 460. 



