918 
Journal o f Agricultural Research 
Vo 1. XXX, No. 10 
in crosses of purple with white the F 2 
generation shows a ratio of 3 purple to 
1 white. 
Linkage relations. —Although con¬ 
siderable work has been done on in¬ 
heritance in barley, comparatively few 
cases of linkage have been shown defin¬ 
itely. Ubisch {23 v. 17, 20) showed a 
correlation between the internode 
length of the rachis and the length of 
the awn. In crosses of varieties with 
long awns and lax spike with varieties 
having short awns and dense spike the 
F 2 results indicated a gametic ratio of 
4 or 5 to 1. In later studies {23, v . 25) 
he obtained a correlation between the 
Jength of awn and naked seed. The 
gametic ration was 1:6. A gametic 
ratio of 1:5 was obtained in the cross of 
varieties having lax spike and naked 
seed with varieties having dense spike 
and covered seed. From these results, 
Ubisch reached the following conclu¬ 
sions: Factors for the length of awn and 
the length of internode are linked with 
16.7 per cent crossovers; factors for the 
length of awn and covered versus naked 
seed are linked with 14.3 per cent cross¬ 
overs; and factors for internode length 
and for covered versus naked seed are 
linked with 16.7 per cent crossovers. 
These results seem inconsistent with 
the linear theory for the arrangement of 
genes in the chromosome. Several 
factors have been found, however, pro¬ 
ducing varying densities of the spike. 
Because of this fact and the absence of a 
careful statistical analysis one is 
hardly justified in drawing definite 
conclusions from these results. Ubisch 
{23, v. 17) also found a linkage between 
the factor for 6-rowed with one of the 
factors for teeth on the glumes. The 
crossover percentage was 16.7. 
A correlation was found by Vavilov 
{25) between the factor for rough awn 
and the factor for naked seed. The 
intensity of the linkage was not 
worked out. 
Nilsson-Ehle {16) showed that one 
of the factor pairs for green versus 
white seedlings (factor pair Cc) is 
correlated with the factor pair for 
green versus chlorina (factor pair Ff). 
In the cross CcFF with CCff he studied 
the progeny of the combination cFX Cf. 
In F 2 he expected a ratio of 9 green : 3 
chlorina : 4 white, and obtained 8.44 : 
3.94 : 3.62, respectively. Instead of the 
normal 1 : 2 : 2 : 4 ratio in F 3 from 
green F 2 plants, he obtained no families 
which bred true for green, 9 families 
which segregated into green and chlorina, 
12 which segregated for green and white 
seedlings, and 126 families which pro¬ 
duced all types. He suggested linkage 
with about 10 per cent crossing over as 
the best explanation. 
In the foregoing review a number of 
character pairs are considered. It 
seems, however, that little has been 
done to establish the relation of these 
character pairs to each other. One of 
the best studies from the standpoint 
of the relation of factors for several 
character pairs is that carried on at 
the Minnesota station in cooperation 
with the Office of Cereal Investigations, 
Bureau of Plant Industry, United States 
Department of Agriculture, and cited 
by Hayes and Garber {8). Four char¬ 
acter pairs were studied in one cross: 
Hooded versus awned, 2-rowed versus 
6-rowed, black versus white seed, and 
hulled versus naked seed. These four 
character pairs were shown to be inde¬ 
pendently inherited or, in other words, 
to represent four linkage groups. 
According to the work of Vavilov 
{25), one of the factors for dentition 
of the awn is correlated with the factors 
for hulled versus naked seed. The 
results obtained by Ubisch {22) indi¬ 
cated that this group also contains a 
factor for length of awn and one for 
length of rachis internode. 
In the present study the various 
character pairs are considered in their 
relation to each other with an idea of 
establishing a linkage group for each 
chromosome pair. 
MATERIAL USED 
All varieties used in these studies are 
known to be pure lines: 
Svanhals is a variety of Hordeum 
distichon. It has white glumes, rough 
awns, headed about July 6, and is 
highly resistant to the spot blotch 
disease caused by Helminthosporium 
sativum. 
Lion is a variety of Hordeum vulgare. 
It has black glumes, smooth awns, 
headed about June 21, and is highly 
susceptible to the spot blotch disease. 
Manchuria, 1-16-66, is a selection 
from Manchuria, a variety of Hordeum 
vulgare. It has white glumes. 
Hordeum deficiens steudelii, as its 
name indicates is a deficiens variety. 
It has black glumes and the lemma 
and palet of the florets in the lateral 
spikelets are developed slightly or 
not at all. 
Hordeum intermedium cornutum is a 
variety of intermedium (4) with practi¬ 
cally complete fertility in the florets of 
the lateral spikelets. The florets of the 
median spikelets are hooded. It is 
hulless and has white seeds. 
The results given here are from the 
crosses Svanhals X Lion and Hordeum 
deficiens steudelii X Manchuria. The 
crosses were made at University Farm, 
St. Paul, Minn., in 1921 and the Fi 
