es) 
al 
tO 
I 
ZIGZAG CULM WITH UPPER AND LOWER 
INTERNODES APPARENTLY NORMAL 
Usually only the internodes in the ear shoot 
region are affected. Note how the leaf sheathes 
stand off at right angles to the affected inter- 
nodes. The plants are apt to break at these 
internodes, but otherwise they appear as vigor- 
ous under field conditions as normal plants. 
(Fig. 10.) 
The Journal of Heredity 
nodes have the leaves attached at op- 
posite sides the result is a more or less 
zigzag stem. 
Extracted recessives from crosses 
vary considerably in the expression of 
the zigzagcharacter. In Figs. 14, 15,and 
16 are shown such extracted recessives. 
The plants shown in Fig. 14 are quite 
distinctly zigzag and somewhat 
dwarfed. The short twist high on the 
stem of the second and third plants in 
Fig. 14 is another plant abnormality 
which will be described in another 
paper. So far as known at present it 
is inherited independently of zigzag 
culm. Other less extreme plants are 
shown in Fig. 15. Suchplantscan very 
easily be recognized when mature by 
stripping away the leaves in the ear 
shoot region. The plants shown in 
Fig. 16 were selected to show how closely 
some zigzag plants approach normal 
plants in appearance. Such plants are 
not perceptibly dwarfed as the inter- 
nodes are only a very little or not at all 
shortened, even in the ear shoot region. 
After some experience such plants can 
easily be identified after removing the 
leaves. It will be noticed that in each 
of the plants shown in Fig. 16a number 
of the internodes are arched away from 
the point of leaf attachment. Com- 
parison of these culms with the culm of 
a normal plant as shown in Fig. 12 will 
make this clear. 
INHERITANCE OF ZIGZAG CULM 
Mention has already been made that 
zigzag culm was found by Dr. Emerson 
to be a recessive character. The writer 
also made many outcrosses with normal 
plants and in every case the F; plants 
were apparently normal. Several F2 
progenies were grown which gave a total 
of 343 normal to 23 zigzag plants. This 
is a very wide departure from a 3:1 re- 
lation which should obtain if zigzag 
culm is a simple mendelian recessive. 
There is, however, a deviation of only 
0.1+3.1 plants from a 15:1 relation ex- 
pected when two factors are concerned 
in the expression of a character. This 
is an exceedingly close fit. In taking 
the notes each plant was entirely de- 
foliated and its culm was carefully ex- 
amined. In spite of the close agree- 
