acters of 4. fatua. ‘Thus it was demonstrated that the 
B-factor is carried on the C-chromosome. Whether or 
not the B-factor is an inhibitor of the 4. fatua-type of 
upper floret-articulation is unknown, as fatuoids have not 
been observed in A. sterilis. 
A. sterilis has the distinction of being the only hexa- 
ploid species which has not been theoretically derived 
from some other hexaploid Avena species now living. If 
it arose independently by allopolyploidy, one can scarcely 
resist suggesting 4. Bruhnsiana, with its large spikelets 
and non-articulated upper florets, as the diploid ancestor. 
Avena byzantina 
The nature of the genetic mechanism controlling the 
grain characters of the cultivated red oat is by no means 
clear. Some forms of this species seem to have both the 
B- and C-factors on the same chromosome. This is true 
of cultivar Fulghum which Florell (1931) crossed with 
A. fatua. The F2 segregated in the ratio of 8 byzantina- 
like to 1 fatua-like for the grain characters. Among the 
478 plants of the F2 were 4 cross-over progeny resembling 
A. steriis and 8 resembling A. sativa. Stanton et al. 
(1926) found fatuoids arising from Fulghum and Burt to 
resemble A. fatua, indicating that the B- and C-factors 
were inhibiting the development of wild-type genes pos- 
sessed by those varieties. 
A. byzantina cultivar Coastblack, however, seems to 
have the B- and C-factors on the same chromosome, as 
well as an additional B-factor on another chromosome. 
In the cross Coastblack XA. fatua Florell (1981) ob- 
tained an F2 ratio of 12 byzantina-like : 8 sterilis-like : 
1 fatua-like for the grain characters. 
Bond, which is said to belong to A. byzantina, has 
no C-factor at all, but has the B-factor, as is shown by 
the work of Hayes et al. (1989), Torrie (1989) and Ko 
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