June 1, 1925 
Variation in the Kherson Oat 
1071 
In 1921 parental florets disarticulat¬ 
ing by semiabscission produced prog¬ 
eny of which two-thirds disarticulated 
by semiabscission and one-third by frac¬ 
ture. Parental florets disart iculating by 
fracture produced progenies in 1921 of 
which one-third disarticulated by semi¬ 
abscission and two-thirds by fracture. 
The results obtained in 1921 indicate 
that a definite relation exists between 
parent and progem- in spikelet disar¬ 
ticulation. Each parental type pro¬ 
duced a much larger percentage of 
progeny spikelets of its own kind of dis¬ 
articulation than of the other type. 
The 1922 data on the inheritance of 
spikelet disarticulation supported the 
conclusions drawn from the 1921 data 
on the inheritance of this character 
in Kherson. Eighteen progeny groups 
were grown in 1922 from parental 
florets disarticulating by semiabscis¬ 
sion. Approximately 67 per cent of 
the progeny disarticulated in the same 
way. In only 4 of the 18 progeny 
groups was less than 50 per cent of the 
spikelet disarticulation by semiabscis¬ 
sion, while in 5 strains more than 90 
per cent, and in 1 group all progeny, 
were so classified. 
Spikelets in which disarticulation was 
by fracture produced progenies in 1922 
of which 81.4 per cent disarticulated by 
fracture and 18.6 per cent by semiab¬ 
scission. The relation between parent 
and progeny for this character appears 
to be a definite one. In 8 of 21 groups 
sown from parental spikelets disarticu¬ 
lating by fracture spikelet disarticula¬ 
tion in all progeny was by fracture, 
while in only 3 of the other 13 groups 
did less than 50 per cent of the progeny 
separate by fracture. From these data 
it seems evident that two types of 
spikelet disarticulation exist in the 
Kherson variety. Both of these ap¬ 
pear to be heritable to a large extent. 
It appears possible to isolate by selec¬ 
tion pure-breeding lines of either type. 
Strains breeding true for spikelet dis¬ 
articulation by fracture appear to be 
more numerous in Kherson than are 
those in which spikelet disarticulation 
is by semiabscission. It is impossible 
to determine the genetic constitution 
of Kherson on the basis of the data pre¬ 
sented, but it appears evident that at 
least two factors are involved in the 
inheritance of spikelet disarticulation. 
The two methods of disarticulation in 
Kherson oat are shown in Plate 3. 
Of the 11 progeny groups grown in 
1923 from parental kernels in which the 
spikelet disarticulated by fracture, 6 
bred true and 2 groups produced prog¬ 
eny of which more than 95 per cent 
were like the parent. One group pro¬ 
duced progeny of which nearly three- 
fourths disarticulated by semiabscis¬ 
sion and one-fourth by fracture. Ap¬ 
proximately 65 and 74 per cent, respec¬ 
tively, of the two remaining groups 
disarticulated the same in progeny as 
in parent. 
Of the 9 groups of kernels in which 
spikelet disarticulation in the 1922 
parental kernels was by semiabscission, 
1 group produced progeny nearly all of 
which disarticulated by fracture, 2 pro¬ 
duced progeny of which about 64 and 
71 per cent, respectively, were of the 
parental description, 3 produced prog¬ 
eny of which approximately 95 per cent 
was like the parent, and in 3 groups 
all progeny were like the parent. 
As a whole in 1923 spikelets in which 
disarticulation was by semiabscission 
produced progenies of which 77.8 per 
cent also disarticulated by semiabscis¬ 
sion and 22.2 per cent by fracture. Of 
the parental kernels in which disar¬ 
ticulation was by fracture 85.9 per cent 
of the progeny was similar, only 14.1 
per cent disarticulating by semiabscis¬ 
sion. Compared with the data obj 
tained the two previous seasons, 
progress toward homozygosity is clearly 
shown. 
FLORET DISJUNCTION • 
Disjunction of the second florets 
from their supporting rachilla seg¬ 
ments is one of the most important 
characters studied, as it is fundamental 
in the classification of Avena. The 
data on this character for 1921, 1922, 
and 1923 are shown in Table II. The 
floret disjunction in the 1921 crop was 
predominantly by disarticulation, al¬ 
though approximately 20 per cent of 
the progeny disjoined by heterofrac¬ 
ture or by basifracture. Except for 
the 1922 data, it might have been 
believed that Kherson was heterozy¬ 
gous for floret disjunction. The 1922 
and 1923 data are similar and show 
conclusively that the second florets of 
the Kherson variety separate by dis¬ 
articulation, the common method in 
the species Avena sativa. 
