3°4 
Journal of Agricultural Research 
Vol. XXV, No. 7 
The length of the fifth leaf from the top also showed a good bimodal 
distribution with the brachytic plants, forming a somewhat intermediate 
grouping, as shown in figure 3. 
The width of the fifth leaf was strictly unimodal, with the dwarf plants 
grouped at the upper end of the scale. There was little difference 
between the normal and brachytic plants with respect to this character, 
as is shown in figure 4. 
From the length and width of the fifth leaf it was possible to formulate 
an expression for leaf shape. This figure has been designated leaf index 
and was obtained by dividing the width by the length. 
The distribution of plants with respect to leaf shape was bimodal, 
with the dwarf class well grouped at the upper end of the scale and the 
brachytic and normal plants occupying the lower end as shown in 
figure 5. 
With respect to the number of tassel branches, 68 per cent of the dwarf 
plants had no branches and the highest number of tassel branches found 
<0 
<50 GO 70 80 
TjETVGr// /A/ 
Fig. 3. —Frequency distribution for length of fifth leaf. Shaded portion, dwarf plants; solid lines, 
brachytic plants; broken lines, normal plants. 
in this group was 6, while the brachytic plants ranged from o to 57 
branches and the normals from o to 44, the latter forming a fairly regular 
distribution, as is shown in figure 6. 
The brachytic and dwarf plants differed little in total number of leaves, 
though both had an appreciably higher number than the normal plants. 
The distribution, however, was unimodal, as is shown in figure 7. 
The relative differences between the segregates with respect to all 
measured characters is shown in figure 8. 
From the character of these distributions it would seem that in the 
case of the dwarf variation a relatively few hereditary elements will 
account for the differences between this and the normal form. The 
behavior of the leaf lengths and shapes is very different from that en¬ 
countered where short, broad leaves of nondwarf stock are crossed with 
relatively long, slender leaves of some other strain. In such cases the 
frequency distributions are unimodal, the indication being that several 
hereditary factors are concerned in the differences between the parents. 
