30 
Journal oj Agricultural Research 
YoL XXX, No. 1 
Table I. — Data on inheritance of three different methods of spikelet disarticulation 
in the progeny of selected kernels of each of nine strains of the Burt oat when 
grown at the Akron Field Station and at the Kansas Agricultural Experiment 
Station in 1920 —Continued 
Kernels in progeny 
Strain number and method of disarticu¬ 
lation in parent kernels 
Number disarticulating 
by— 
Percentage disarticulating 
by- 
Abscis¬ 
sion 
Semiab¬ 
scission 
Fracture 
Abscis¬ 
sion 
Semiab¬ 
scission 
Fracture 
KANSAS AGRICULTURAL EXPERIMENT 
station— continued 
Kansas No. 6094: 
Abscission__ ... 
150 
3 
13 
90.4 
1.8 
7.8 
Semiabscission_ .... 
25 
63 
73 
15. 5 
39. 1 
45. 4 
Fracture_ 
3 
205 
348 
. 5 
36. 9 
62.6 
All 9 strains: 
Abscission_ 
1,570 
759 
140 
63.6 
30. 7 
5. 7 
Semiabscission.. ... . ..._ _ 
512 
839 
804 
23.8 
38.9 
37.3 
Fracture_ . 
289 
974 
6,195 
3.9 
13.0 
83. 1 
BOTH STATIONS 
Abscission__ 
6, 979 
803 
2,990 
914 
814 
64. 7 
27.7 
7.6 
Semiabscission_ 
806 
31.8 
36. 2 
32.0 
Fracture_ 
1,513 
4, 641 
19,670 
5. 8 
18.0 
76.2 
disarticulation was impossible and no 
data on this character are included.) 
The abscission type bred true in 92.4 
per cent of the kernels grown from pa¬ 
rental kernels described as disarticu¬ 
lating by this method. 
The parental kernels in which spike- 
let disarticulation was classed as re¬ 
sulting from semiabscission, produced 
progeny containing approximately three 
individuals in which spikelet disartic¬ 
ulation occurred by semiabscission or 
fracture to one by abscission. The 
parental kernels in whfch spikelet dis¬ 
articulation was described as fracture, 
produced progeny of which the spikelet 
disarticulation was 64.3 per cent by 
fracture, 33.2 per cent by semiabscis¬ 
sion, and 2.5 per cent by abscission. 
It would appear from the 1921 data 
on the inheritance of spikelet disarticu¬ 
lation that in the Burt oat the spikelet 
disarticulation by fracture is dominant 
and that by abscission recessive. The 
class here described as resulting by 
semiabscission possibly represents the 
heterozygous group. These results 
seem to be in general agreement with 
those of Surface ( 127), Love and 
Craig (70), and Fraser (37), who 
studied the inheritance of the basal 
scar as an expression of this character. 
The results obtained agree with those 
of previous investigators and indicate 
that spikelet disarticulation behaves 
as a simple monohybrid. Fracture 
or the absence of basal cavity probably 
is dominant, or at least partially so, 
over abscission or presence of a basal 
cavity which seems to behave as a 
recessive. 
Etheridge (33) believed that the 
basal cavity is of little use in classifying 
oat varieties. The results of many inves¬ 
tigators indicate that this character 
is of distinct value in classifying oats 
and that it is more or less constant 
in its breeding behavior. This char¬ 
acter has been much used in distin¬ 
guishing oat varieties of the Arena 
byzantina group from those of the 
sativa group and it is thought to be of 
more value than the statement of 
Etheridge would indicate. 
FLORET DISJUNCTION 
The floret disjunction classes pre¬ 
viously described are disarticulation 
(as in A. sativa), heterofracture, and 
basifracture (as in A. byzantina). 
These three ways by which floret dis¬ 
junction takes place are illustrated in 
Plate 1, D to F, inclusive. The term 
heterofracture was used for the method 
of disjunction of those florets or kernels 
in which the rachilla segment broke 
variously at or near the midpoint, as 
shown in Plate 1, E. In these cases 
part of the rachilla remained with the 
primary kernel of the spikelet and 
part of it broke off with the secondary 
kernel. 
