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. 1+61}. Many of the variations are 

 conspicuous, while others are discovered only through close 

 inspection. Some variations better adjust the individual to its 



FIG. 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 



