AGRICULTURAL BOTANY 167 



induce uniformity after he has secured the variation 

 he wishes, that is, he is trying to fix the variation. 

 Variation can in some cases be induced : 



1. By culture. Change of food and climate will work 

 changes from the parent plant little short of marvelous. 



2. By growing seedlings. This method is used with 

 plants which have usually been propagated by budding, 

 grafting, or division (like dahlias). Characteristics of 

 the parent plant are more variable than those of varieties 

 grown from seed, therefore the young seedlings will 

 show differences. Desirable individuals among these 

 may be chosen for fixing. 



3. By cross-pollination. (See page 147.) This method 

 will work changes from the parent type nothing less than 

 wonderful. Burbank has secured some marvelous results 

 largely through this method. The individual plants 

 produced from the two parent plants are not exactly 

 like either, neither are they like each other. Some of 

 them resemble one parent in a marked degree and some 

 of them the other. It is quite within the probabilities 

 that scientific breeding by cross-pollination will be able 

 to produce individuals that have only the best charac- 

 teristics of each of the parent plants and that the seeds 

 of these individuals may be used to perpetuate the 

 variety. 



To insure the best results, the plant breeder should 

 have clearly in mind the characteristics which he desires 

 to secure in his new variety, and then select the two 

 parents with care. 



A wise selection is the plant breeder's most potent 

 factor in securing uniformity and thus improving his 

 crops. This means the rejection of many individuals 

 and the retention of a few desirable ones from which 



