842 
Journal of Agricultural Research 
Vol. XXVIII, No. 
Table I .—Showing the segregation in F 2 for beards and pubescent nodes 
Pubescent node 
Glabrous node 
Beardless 
Bearded 
Beardless 
Bearded 
Observed__________ 
468 
453.5 
202 
226. 75 
237 
226. 75 
°o 
Calculated 2:1:1__..... 
Deviation____ 
14.5 
24. 75 
10.25 
0 
These results show that there were no bearded plants with glabrous nodes* 
The presence of beards usually is due to one factor for beards and the ratio 
obtained usually is 3 beardless to 1 bearded, and the pubescent-node character 
occurs in the simple 3 : 1 ratio with pubescence dominant, as described above. 
Therefore, when the grouping is made according to the two characters one would 
expect to obtain some plants that were bearded with glabrous nodes unless linkage 
occurs. In this case the data seem to indicate that there may be a linkage 
between beards and pubescent nodes. These two characters come in together 
and out of 907 plants there is not a single case of a crossover type. This also 
may suggest that beards and hairy nodes result from one factor and that the 
difference between the parent forms is due to one factor pair. For the present 
such an assumption will be made. 
In respect to the node character the Velvetnode variety may be designated 
by VV and the beardless strain with glabrous nodes by vv. The F t gametes 
may then be represented by Vv. In F 2 there will be the following types and in 
the ratio indicated:—1 VV: 2 Vv: 1 vv. The numbers obtained deviated some¬ 
what from the calculated numbers and the value of P is 0.168, which does not 
indicate a very good fit. When the different plants are tested in F 3 , however, 
it seems that the facts support this 1:2:1 assumption. There are certain 
exceptions that will be mentioned later. 
According to this assumption, the bearded plants with pubescent nodes ( VV ) 
all will breed true; the same is true also for the beardless plants with glabrous 
nodes (vv). The beardless hairy-noded plants (Vv) all should segregate again 
into the three types. 
Of the F 2 plants, 238 were chosen for testing in the F 3 . The numbers from the 
different classes were as follows: 123 beardless with pubescent nodes, 68 bearded 
with pubescent nodes, 47 beardless with glabrous nodes. 
From the F 2 generation, 123 plants that were beardless with pubescent nodes 
were tested in F 3 . According to the above assumption these would be expected 
to segregate into beardless glabrous, beardless pubescent, and bearded pubescent, 
in the ratio of 1 : 2 : 1. Of these plants, 117 segregated in this manner, and, 
while the number of individuals is not large in some of the families, yet the 
total number of plants is rather large. The total number is 1,295 beardless 
glabrous, 2,524 beardless pubescent, and 1,158 bearded pubescent. The cal¬ 
culated numbers for the three classes are 1,244.25 : 2,488.50 : 1,244.25. 
There is considerable difference between the calculated and observed numbers. 
Part of this may be due to the fact that some plants became very ripe in the 
field before they were harvested (all the notes were taken in the field), and 
owing to the shattering of some of the awns or beards it was difficult at times to 
be sure a plant was bearded. The value of P in this case is only about 0.014, 
which shows a poor fit for a case of this sort. If it were not for the breeding 
behavior, one would conclude that the deviation from expectancy was too great 
to substantiate the hypothesis assumed. 
