Ernest AVarren 
111 
{E). In Series III a dark-coloured homozygous dominant plant {B) was also 
crossed with a white plant. One of the darkest heterozygous offspring {B x White) 
pi. 1 was selfed and the coloured plants raised tended to be paler than the grand- 
parent, but the family was small. 
In Series IV the dark-coloured homozygous plant (B) was crossed with a dark 
heterozygous plant (^1). From the offspi'ing raised, two were selected and selfed, 
one very dark and the other moderately dark. The two families included only 
coloured plants, and consequently the parents may be supposed to have been 
homozygous. The moderately dark parent {B x A) pi. 2 failed to produce any 
offspring as dark as the grandparent {B). 
In Series V the same plant {B) was crossed with a light heterozygous plant 
(C). From the offspring produced five homozygous dominants were selfed, and in 
the five families raised only two plants reached the colour-intensity of the grand- 
parent {B). 
On taking all these results together it may be said that there is evidence for 
the view that crossing a dark race of foxgloves with white plants tends to dull the 
colour-intensity of homozygous dominants of subsequent generations. 
General Coloration — Strength of Inheritance and Effect of Selection. 
In 1914 a dark-coloured homozygous plant (^4 $ ) was crossed with a somewhat 
pale-coloured heterozygous plant (Cj </) = DZ) x = III. The offspring would 
consist theoretically of approximately equal numbers of dominants and hetero- 
zygous individuals. The reciprocal cross (C, $ x B^cf) was also made = II. Several 
dominants were selfed and families were raised. Out of these families certain 
plants were selected and selfed and new fixmilies werQ obtained. This procedure 
was continued until 1917, and the results are given in the accompanying table. 
The families of the different years are arranged in ascending order of the colour- 
intensities of the parents. On comparing the means of the families with the 
colour-grade of the parents (shown in brackets) it will be at once seen that small 
variations in the colour-intensity of the parents tended to be transmitted to the 
offspring. It is obvious that the table exhibits the effect of selection in self- 
fertilised homozygous generations. 
For example we may take the following : 
Homozygous plant, IT. 1 had a colour of 70 and a mean of offsprino; 74 
An oftkpi'iiig of above, IT. 1, 4 „ 74 „ „ ,, 82 
A71 offspring of above, II. 1, 4, 17 „ „ 110 „ „ ,, 95 
Homozygous plant, III. 2 „ „ 75 ,, „ 66 
All offspring of above. III. 2, 1 „ „ 66 ,, ,, ,, 55 
An offspring of above, III. 2, 1, 18 „ „ '«) „ ,, „ 85 
An offspring of above, III. 2, 1, 18, 28 „ „ 95 „ „ „ 100 
Reverse selection is shown also : 
Homozygous plant, TIT. 2 „ „ 75 „ „ „ 66 
An offspring of above, III. 2, 5 „ „ 52 „ „ ,, 57 
An off'spring of above, III. 2, 5, 5 „ „ 40 „ „ „ 41 
An offspring of above. III. 2, 5, 5, 12 „ „ .30 „ „ „ .32 
