May 24,1924 Inheritance of Pubescent Nodes in Wheat Hybrids 
843 
In addition to these 117 plants there were certain ones that showed a different 
behavior. For example, there were four F 2 beardless plants with pubescent 
nodes whose progeny did not segregate into the three groups as did those of the 
117 plants noted above. Two of these plants produced plants with hairy nodes 
only, but segregated for beards. These produced 76 plants that were beardless 
with pubescent nodes and 20 plants that were bearded with pubescent nodes. 
While these numbers are not large, nevertheless in other cases with smaller num¬ 
bers the expected 1:2:1 ratio was obtained or approached. The other two F a 
plants produced only beardless plants in F3, but segregated for pubescent and 
glabrous nodes. 
Thus, out of 123 plants of the F 2 , 117 reproduced the three types in the expected 
ratio, 1:2:1, that would follow providing the difference between the parent forms 
is due to one pair of factors. The occurrence of these six plants that did not 
give the expected ratio suggests that there may be more than one pair of factors 
concerned. 
From the F 2 generation 68 plants that were bearded and had pubescent nodes 
were selected to test in F 3 . All of the 68 plants bred true to the type selected; 
that is, all plants produced were bearded with hairy nodes. 
There also were 47 beardless plants with glabrous nodes selected from the F a 
generation to test in F 3 . All but two of these plants produced beardless plants 
with glabrous nodes. 
The possibility that more than one pair of factors is concerned is further em¬ 
phasized by the fact that there were two F 2 plants classed as beardless with 
glabrous nodes that did not breed true to this character, as would be expected, 
but segregated for beards. These produced 38 beardless plants with glabrous 
nodes and 19 bearded plants with glabrous nodes. While in the F 2 no bearded 
plants with glabrous nodes were obtained, yet in F 3 it is seen that some plants 
of this class do occur occasionally. 
In addition to the plants whose behavior in F 3 is cited above, there were five 
that produced some bearded plants with glabrous nodes, but the numbers were 
so small that it may be questioned whether they may not be accidental crosses or 
mixtures of some kind. These plants are being tested further. 
The six F 2 plants that have been mentioned as giving ratios differing from the 
expected ratios may be crossovers; and, if so, the genetic constitution assumed 
would have to be modified. A very close linkage would be indicated and the 
difference between the parent forms would be considered as due to two pairs of 
factors rather than one. It may be possible that these six aberrant plants result 
from natural hybridization in the field. This, however, is rather unlikely as no 
simple cross will explain certain of the results. For example, take the case of the 
two plants that produced all beardless plants in F 3 , but segregated for pubescent 
and glabrous nodes. As a 3:1 ratio for node type was obtained, it is difficult to 
see how this could arise from hybridization. If true-breeding pubescent-noded 
beardless types existed, this could be explained by a cross with a beardless 
glabrous-noded type, but so far no such constant type has been found. 
It does not seem wise to conclude that natural crossing may be the cause of 
these few plants which produce different ratios from the majority of plants found 
in the same F 2 classes. 
It is possible that they may be explained by mutations occurring in the germ 
cells, but at present no attempt will be made to assign a definite cause. After 
further breeding tests, now under way, are finished, a definite explanation can 
be given. 
The plants of F 2 and F 3 also were classified for pubescent glume to determine 
whether this character segregated independently. The distribution of the F 2 
