12 
Journal oj Agricultural Research 
Vol. XXX, No. 1 
as distinguishing characters in their 
classifications of oats. Schulz also is 
cited as having used the character of 
the rachilla connection to differentiate 
Avena sterilis from A vena fatua, A vena 
barbata, and Avena wiestii. 
Von Tschermak (137) describes the 
linkage groups observed in crosses be¬ 
tween cultivated and wild oats. There 
is absolute coupling between brittle¬ 
ness, or the falling apart of the spikelet 
on ripening, and complete beardedness. 
There is complete incompatibility of 
stiff hairs on the lemmas, as in the wild 
oat, and the yellow color of the culti¬ 
vated oat. Brown floret color, as in 
the wild oat, and the glabrousness of 
the cultivated oat also are incompati¬ 
ble. 
Wiggans 13 studied the breeding be¬ 
havior of the rachilla character in a 
cross between Red Texas and Swedish 
Select oats. The rachilla disjunction 
of the Fi kernels was very similar to 
that of the Red Texas parent, each 
rachilla segment remaining attached to 
the base of its floret- when threshed. 
This character is more definite than the 
basal connection, but in F 2 all grada¬ 
tions from the typical Red Texas dis¬ 
junction to the typical Swedish Select 
were found. The Red Texas type of 
disjunction was dominant, and it seems 
fairly certain that the kind of disjunc¬ 
tion is determined by one pair of fac¬ 
tors. 
Fraser (37) has reported a cross of 
Burt and Sixty-Day in which he found 
that the “non-Burt” type of disjunc¬ 
tion was dominant to the “Burt” type. 
He states that the Burt type is similar 
to that of Avena sterilis. He found 
that three non-Burt plants with the 
disjunction appeared in F 2 to one with 
the Burt form. Fraser also found 
linkage between the Burt disjunction 
type and the fully awned condition, 
4.14 per cent of crossovers being found 
in 2,341 individuals. He states that 
the Burt oat used as parental material 
had the A. sterilis disjunction type, 
while the Sixty-Day had the usual A. 
sativa characters in all respects. 
BASAL HAIRS 
Basal pubescence or the hairs borne 
on the callus at the base of the oat 
floret has been'given varying amounts 
of attention by different investigators. 
Nilsson-Ehle (90) observed that cer¬ 
tain oat varieties had long hairs on the 
callus, others had short hairs, while 
still other forms had few or no hairs. 
When a long-haired form was crossed 
with a short-haired form, the resulting 
recombination produced some indivi¬ 
duals having no basal hairs and others 
having stouter hairs than either parent. 
The hairs of the rachilla were found to 
be inherited quite independently of 
the basal hairs. 
Zade (153), in discussing the results 
obtained from a cross of Avena fatua 
by Avena sativa, states that Fi was in¬ 
termediate and that the F 2 showed the 
two parental and the intermediate 
types of basal hairs. The progeny 
segregated in a 1 : 2 : 1 ratio. 
Trabut (135) makes use of the char¬ 
acter of basal hairs in tracing the origin 
of cultivated forms from the wild oat 
species. 
Etheridge (33) in reviewing the work 
of previous systematists states that 
the basal hairs frequently are employed 
by botanists, notably Hitchcock (52) 
and Britton and Brown (11), in charac¬ 
terizing Avena species. He states that 
Denaiffe and Sirodot (26) are the only 
authors who have made definite use of 
the basal hairs in classifying cultivated 
forms of Avena, although Bohmer (10), 
Broili (12), and Fruwirth (38) men¬ 
tioned this character in discussing the 
morphology of the oat floret and dis¬ 
tinguished types of basal hairs on the 
basis of differences in their form and 
frequency. In his classification of 
oats, Etheridge uses a modification of 
the systems of Broili and Fruwirth. 
Fischer (35), according to Etheridge, 
holds that the hairs on the base of the 
oat kernel are a mark of degeneration, 
and that they occur more often in the 
winter varieties than in others. 
Surface (127), reporting on the cross 
Avena fatua X Avena sativa, variety 
Kherson, states that jn Fi basal pubes¬ 
cence was present and the base form 
was intermediate but more closely re¬ 
sembled that of the sativa parent. With 
regard to the Fi of this cross he states 
that the lower floret is pubescent on 
the back but the upper is entirely glab¬ 
rous. There is a fairly heavy tuft of 
hair at the sides of the base of the lower 
floret but none on the upper. Surface 
also found that there was correlation 
between the “wild” base and heavy 
pubescence on all sides of the upper 
floret. He also found that pubescence 
on all sides of the low~er floret of the 
spikelet was correlated with the “wild” 
type of base. 
Fruwirth (39) found that the basal 
hairs on the oat kernel are rather con¬ 
stant in breeding behavior, and that 
selections for nine years did not effect 
any change in the density or length of 
the basal hairs. 
13 Wiggans, R. G. op cit. 
