IMPROVEMENT OF PLANTS AND ANIMALS 



FIG. 4. Heights of a thousand men arranged in order. The great majority 

 differ by small amounts. There are a few giants and a few dwarfs 



tendency to vary may be said to be one of the characters 

 that is inherited. 



9. Natural Selection. There is room in the world for 

 only a small proportion of the plants and animals that 

 begin Hfe. A single corn plant usually has five hun- 

 dred to a thousand kernels. If all were planted and 

 grew, the entire world would soon be a corn-field. A 

 morning-glory plant may produce several thousand seeds. 

 A puff-ball produces millions of spores, each of which is 

 ready to grow if given proper conditions. Since the total 

 number of plants cannot greatly increase, it is evident 

 that only a few of the hundreds or thousands of seeds 

 produced by one plant can grow. All the others must be 

 crowded out. If a thousand plants come up where there 

 is room for but one, the strong will overshadow the weak 



Fio. 5. Egg production of 63 hens for one year. The number varied from 

 none to 170 



