INHERITANCE 519 
number of leaves or flowers, time of maturing, character of root 
system, etc. The individuals of a group of organisms not only 
differ from each other, but they also differ just as strikingly 
from their parents. Even the organs of the same plant, such 
as leaves, vary widely (Fig. 467). Many of the variations are 
conspicuous, while others are discovered only through close 
inspection. Some variations better adjust the individual to its 
Fic. 467. — A number of Mulberry leaves selected from the same tree 
to show variation in form. 
surroundings, others are detrimental, and some are neither use- 
ful nor detrimental. Darwin’s idea was that variations, which 
are innumerable and various in kind, afford ample material 
upon which natural selection can work. Why plants and ani- 
mals vary, Darwin did not attempt to explain. 
Inheritance. — Although it is common observation that off- 
spring and parents differ, it is also common observation that 
there are always some fundamental resemblances. Thus the 
offspring of a given variety of Corn are the same in variety as 
