On the mode of Inheritance of certain Characters etc. 301 
sation by this other strain may have occured and have escaped 
detection. In the case of the sulphur-white strain the evidence 
indicating an excess of doubles is equally strong. Here 62 families 
were recorded. Two in which only 2 plants — a single and a double 
— were included may be left out of account. Of the remaining 
60 families 52 gave an excess of doubles. In the remaining 8 families 
the preponderance of singles never amounted to more than 2 except 
in two of the smallest where the totals (3 and 7) are obviously too 
small to be conclusive. The evidence from the other glabrous double- 
throwing strains in which fewer families were raised points to the 
same conclusion and more recently confirmatory evidence has been 
obtained from certain hoary strains. During the present season three 
families of hoary whites have been flowered. The numbers obtained are 
single double 
119 135 
12 170 
65 83 
As we might expect there is the same preponderance of doubles here 
as in the glabrous types. The excess of doubles in an eversporting 
form in fact is as undeniable as the excess of hoary plants in an F, 
family from 2 glabrous parents, where F, is hoary and heterozygous 
in any two of the four factors required to produce hoariness: or as 
the excess of sap-coloured plants in an F, family from 2 non-sap- 
coloured parents where F, is heterozygous in the two factors for sap 
colour. Any theory therefore which claims to explain the method 
of inheritance of these characters in Stocks must take into account 
this ratio of inequality as much in the case of the character which 
shows sex-limited inheritance as in those which do not. 
In the scheme which I have formulated this fundamental fact is 
accounted for in the following way. It is assumed 
(1) That singleness is due to the presence of two factors. 
(2) That these two factors exhibit “partial coupling”, the coupling 
being probably either on a 7:1:1:7 or a 15:1:1:15 basis. 
(3) That the male gamete is unable to carry these two factors(t). 
As regards the first assumption (presence of 2 factors). It has 
already been shown in the course of these experiments that in the case 
of at least two other characters in Stocks, viz. condition of hoariness 
and presence of sap-colour, the dominant condition (hoariness, and 
coloured sap) is in each case due to the presence of a fair of factors 
(1) For a fuller statement of the case see Journ. of Genetics, Vol. 1 No 4. p. 321. 
