CHAPTER THIRTY 



VARIATIONS AND MUTATIONS 



No two fruits, flowers, or other plant organs are exactly alike. 

 The variations may be small or large, and there may be every 

 gradation between the extremes of any character. The several 

 thousand sunflowers that might be grown from a pound of seed 

 would vary in height of stem, amount of branching, and size 

 of flowers. Not only may there be variations in the structures 

 of plants, but there may also be variations in the composition of 

 the plant organs. For example, the great variety of colors, flavors, 

 and other qualities of apples is due to variations in the chemical 

 composition of this fruit. The variation in each of these char- 

 acters is quite independent of variations in other characters. A 

 thorough knowledge of the possible kinds of variations that 

 occur in plants is a necessary preliminary to progress in dis- 

 covering their causes and in utilizing them in plant breeding. 



Variations due to environ- 

 ment. Many variations are 

 due to the environment. When 

 a crop plant like corn is grown 

 in rich soil and in poor soil, 

 there are great differences in 

 the size of the plants and in 

 the yield per acre. These 

 variations in size and yield are 

 due to the environment. Even 

 though the seed planted in 

 each kind of soil is exactly the 

 same, there will be wide dif- 

 ferences in the plants. Ex- 

 amples of these variations 

 were discussed in the chapters 

 on ecological variations of 

 280 



Fig. 178. Two plants of sweet corn of the 

 same variety, one grown in poor soil and 

 one in soil to which fertilizer was added. 

 The differences in the plants are due to the 

 environment. 



