PLANT BREEDING 191 



books. Careful study of the gardens or fields of some suc- 

 cessful breeder is also necessary. The five rules which follow 

 are here given only to illustrate some of the precautions 

 necessary to insure success. 



1. For breeding experiments choose plants like wheat, corn, 

 and apples, which naturally show many varieties or elementary 

 species (fig. 163). 



2. Breed for one 

 character at a time ; 

 that is, do not try 

 to get such a prod- 

 uct as a strawberry 



which shall surpass FlG- 168- Four extremelv unlike varieties of apple 

 selected from thirty- six varieties, all seedlings of 

 most others in size, the Early Williams apple 



Sweetness, bearing Modified from photograph by Burbank 



qualities, and abil- 

 ity to stand shipping long distances all the desirable quali- 

 ties in one berry. 



3. Do not try to get opposite qualities in the same breed. 

 For instance, corn cannot be bred for high percentage of 

 starch and of protein at the same time. 



4. Choose plants for seed by inspection as they grow in 

 the field. A melon or a cucumber plant which bears many 

 rather large fruits is likely to be a better parent than a plant 

 which bore only one very large fruit. The total product of the 

 individual should be ascertained by field study, and the vigor 

 and general condition of the plant should be carefully noted. 



5. Keep up the type by constant selection of the best indi- 

 viduals for seed, even after breeding has resulted in securing 

 plants that come up to the desired standard. This is abso- 

 lutely necessary in perpetuating, for instance, the variations 

 which make the difference between the sweetest and the 

 poorest sugar beets ; but it is also useful in keeping such 

 elementary species as wheat varieties up to the highest stand- 

 ard, because the seed of a desirable variety might be taken 

 from imperfect or diseased ears and yield a poor crop. 



