Variations and Mutations 2S3 



of each are inherited and appears in successive generations. 

 Heritable variations are the result either of mutation or of 

 hybridization. 



It is possible to get all kinds of combinations of different char- 

 acters, and by careful hybridizing and selection to combine many 

 desirable qualities in a single plant. The Shasta daisy, for ex- 

 ample, was made by breeding together the English, American, 

 and Japanese daisies, and combining in one plant the pleasing 

 foliage of the English species, the free-blooming habit of the Amer- 

 ican daisy, and the waxy luster of the petals of the Japanese plant. 



Variations of all kinds are of interest to the plant breeder, 

 because he must learn to distinguish between the two kinds. His 

 attempts to develop a new variety from plants having certain 

 qualities will be futile unless he is dealing with heritable varia- 

 tions. It is not always a simple matter to discover the nature 

 of a particular variation. It may require careful breeding ex- 

 periments carried through several generations to determine 

 whether a variation is due to environment, to heritable causes, 

 or to internal non-heritable causes. 



Mutations. Sometimes, among many thousands of individuals 

 a single plant appears which is markedly different from all the 

 others. For example, a few years ago a sunflower was discovered 

 that had some red pigment near the base of the otherwise yellow 

 corollas. Among the millions of sunflowers that have been seen, 

 this was the first one in which a red color was noticed. In some 

 unknown way there was produced in this plant a red pigment not 

 formed in other sunflowers. From the seeds of this plant there 

 were developed other plants having red pigment in their flowers. 

 Evidently the new character is inherited and these sunflowers 

 have a chemical constitution which enables red pigment as well 

 as yellow to be formed. The sudden appearance of the sun- 

 flower with the red pigment is an example of mutation. Indi- 

 viduals that first show new characters are called mutants (Latin : 

 mutare, to change). 



