GENETICS: F. M. SURFACE 
483 
the character pubescence on the back of the upper grain, is correlated 
with other characters. 
Table 3 shows the relation between this character and the type of 
base on the lower grain. In this table the cultivated and intermediate 
types of base are grouped together under the term 'cultivated.' 
It is seen at once that there is distinct evidence of hnkage between 
these two genes. Since the ratio in the non-black plants is disturbed 
by interdependence of two genes, it is necessary, in considering the 
question of linkage, to use the data from black plants only as given in 
the second line of the table. 
Calculating the probable gametic ratio necessary to produce such an 
F2 generation (using the black plants only) it is found that this ratio is 
approximately 65 to 1. 
To sum up the main features of the present hypothesis, it is found that 
the gene for pubescence on the back of the upper grain segregates inde- 
pendently of the gene for pubescence on the back of the lower grain. 
TABLE 3 
Relation Between the Pubescence on the Back of the Upper Grain and the 
Character of the Base 
Cultivated 
Wild 
SMOOTH 
PUBESCENT 
SMOOTH 
PUBESCENT 
All plants 
352 
2 
27 
85 
257 
2 
3 
85 
However, the former gene is unable to produce a pubescence unless the 
factor for pubescence on the lower grain is present in the same zygote. 
The gene for pubescence on the back of the lower grain shows partial 
linkage with the gene for black color. The gametic ratio is apparently 
about 150 to 1. The gene for pubescence on the back of the upper 
grain is partially linked with the gene for the wild base. The gametic 
ratio in this case is approximately 65 to 1. It is very probable that 
these gametic ratios will be changed somewhat when larger numbers 
of individuals are available. It is believed that the present assumption 
represents the essential facts. 
The brilliant work of Morgan and his collaborators upon linkage and 
its relation to the chromosome theory of inheritance makes it exceedingly 
attractive to point out the possible relation of these genes to the chro- 
mosomes. In the first place it has been shown by Nilsson-Ehle (1909) 
and partly by the present work that the three pairs of color genes segre- 
gate independently of each other. It may, therefore, be supposed that 
