June 1, 1925 
Variation in the Kherson Oat 
1067 
separate readily in threshing, but the 
rachilla segment tears away at or 
near its base. At other times dis¬ 
junction may result by the connecting 
segment splitting lengthwise or break¬ 
ing at or near the mid-point. 
Floret disjunction in this study was 
described as resulting by disarticula¬ 
tion when the separation left the 
rachilla segment attached to the face 
of the lower floret; by heterofracture 
when the rachilla segment broke at or 
near the mid-point, making exact 
classification in either of the other 
classes impossible; and by basifracture 
when the rachilla broke off at the base 
and remained attached to the second 
floret. 
BASAL HAIRS 
Most species of wild oats are charac¬ 
terized by hairiness of the lemma, cal¬ 
lus, and rachilla. The callus often 
bears more or less conspicuous hairs or 
bristles, usually conveniently called 
basal hairs. Their presence may be 
observed readily without magnification. 
These hairs vary in number and length. 
Different authors have classified them 
in different ways, but all have used the 
length or number or combinations of 
these in making their classifications. 
In the Kherson variety all hairs are 
short, with but few exceptions. On an 
occasional individual they might be 
termed midlength, but none observed 
were of sufficient length to be classed 
as long. As a result classification of 
basal hairs in the present study is based 
almost entirely on numbers of hairs. 
The occasional kernel with midlength 
hairs was arbitrarily thrown into the 
class with short hairs. All gradations 
from the very shortest hairs visible to 
the eye up to those of midlength were 
observed. In this study of Kherson 
the basal hairs were described as 
abundant, few, and absent. 
AWNS 
In Avena the awn is an extension of 
the midrib of the lemma arising from 
the epidermis at a point usually 
slightly above the middle of the dorsal 
surface of the kernel. In the various 
wild forms awns also occur on the 
second and third kernels. In such 
forms the awn usually is stout and long 
and the basal portion strongly twisted 
in a clockwise direction. The upper 
portion usually is bent or geniculate. 
In most of our cultivated varieties the 
awn occurs on only the lower kernel of 
the spikelet, which may be twisted or 
nontwisted and straight. In prac- 
52243—25t-6 
tically all the varieties of Avena sativa 
the awn occurs only on the lower 
lemma, and there are some varieties in 
which awns occur only occasionally or 
rarely even on the lower floret. In the 
varieties of A. byzantina awns often 
occur on both florets, and in the less 
variable varieties such as Red Rust¬ 
proof and Red Algerian the awn usu¬ 
ally is straight and rarely twisted. 
Trabut {22, 23) observed a series of 
oat forms ranging from the wild red 
oat, A. sterilis, to the cultivated red 
oat which he called A. sterilis culta, and 
noted gradual reduction in the number 
of awns per spikelet and in the amount 
of twisting and geniculation. The 
occurrence of numerous twisted genicu¬ 
late awns in cultivated oats is believed 
by some to indicate degeneracy result¬ 
ing primarily from an unfavorable 
environment. 
Various authors have used different 
terms to describe the nature of the 
awn. Etheridge (5) used the following 
terms: Twisted geniculate, strong, and 
weak. Fraser (6) in his studies of the 
inheritance of what he called the weak 
awn in certain oat crosses used the 
terms strong, intermediate, and weak 
to designate different awn types.. 
The following terms, indicating four 
classes, have been used in the present 
investigations: Twisted; nontwisted, 
long; nontwisted, short; and absent 
(awnless) (pi. 2). While the twisted 
geniculate awn usually is associated 
with wild forms, some cultivated 
varieties, such as Swedish Select, 
frequently show this type of awn to a 
marked degree. In the present study 
all awns showing some twisting were 
classed as twisted, regardless of the 
degree of geniculation. The non¬ 
twisted long awns often were, as long 
as the twisted awns but were never 
twisted. The nontwisted short awns 
varied from approximately 15 mm. in 
length to mere bristlelike appendages. 
LEMMA COLOR 
In oat varieties the lemma varies in 
color. The principal colors recognized 
in descriptions of oat lemmas are 
black, red, gray, yellow, and white. 
Lemma colors in the Kherson variety 
were described in this study as red¬ 
dish yellow, or orange, yellow, and 
white. Lemmas called reddish yellow 
are of a dark orange or reddish color. 
The yellow class included all lemmas 
showing yellow color and varied from a 
rich cream to dark lemon-yellow. 
Lemmas classed as white were of an 
ivory or light cream color. Pure white 
lemmas probably do not exist in oats. 
