652 PHARMACEUTICAL BOTANY 
yellow color and smooth surface; 3 with homozygous characters 2 
for the recessive factor of green color but either homozygous or 
heterozygous for the dominant factor of smooth surface and thus 
all appearing with green color and smooth surface; 3 with homo- 
zygous characters-for-the recessive factors of wrinkled surface 
but either homozygous or heterozygous for yellow color; and 1 
with both sets of characters homozygous for the recessive green 
color and wrinkled surface which breed true when self-fertilized. 
The four classes when grouped as to the appearance of seeds are 
then as follows: 
9 Yellow color, smooth surface 
3 Yellow color, wrinkled surface 
3 Green color, smooth surface 
1 Green color, wrinkled surface 
Ga.ton’s Law or ANCESTRAL INHERITANCE.—Francis Galton | 
was the founder of the scientific study of inheritance. He 
concluded from a study of several selected traits of certain families 
that the two parents contribute between them on the average 
one-half of each inherited faculty, each of them contributing one- 
quarter of it. The four grandparents contribute between them 
one-quarter, or each of them one-sixteenth; and so on, the sum 
of the series } plus 14 plus 1 plus 144 . . . being equal to 1. 
VARIATIONS 
VaRIATIONs represent the differences which exist between the 
individuals of a species. They are those changes in organisms 
which make them different from their parents or from their 
species. No two organisms of any species are exactly alike. 
This is very apparent from the examination of children in the 
same family or plants reared from seeds of the same fruit. 
While having similar characteristics in the main, differences 
may readily be made out whereby we can distinguish the indi- 
viduals. Examples of kinds of variations are variations in size, _ 
symmetry, outline of organs as leaves, the appearance of a new _ 
Pigment, etc. 
Other "kinds of variations are (a) modifications due to differences 
in environment to which organisms are exposed; these are _ 
