CHAPTER III 



PRINCIPLES OF PLANT BREEDING AND THEIR APPLI- 

 CATION IN GARDEN AND ORCHARD 



By plant breeding is meant the systematic raising or repro- 

 duction of plants either with or without an aim toward improve- 

 ment. When gardeners or orchardists observe certain individuals 

 or types with characteristics which should be perpetuated, they 

 may select these individual plants for breeding purposes. The 

 points observed will probably be more or less noticeable in the 

 offspring. 



Causes of Variation. — It is said that no two plants are exactly 

 alike. There is constant variation in nature between individuals 

 even of the same kind. These differences may be noticeable or not 

 by the grower. This tendency to vary from each other makes it 

 possible for the plant breeder to select characteristics which he 

 desires. This gives rise to new varieties and new strains. Careful 

 observation is required to select the desired types. It is necessary 

 to keep these ideals constantly in mind in establishing newvarieties. 



Among the causes which tend to make plants vary may be 

 mentioned (1) shade and sunlight, (2) differences in soil and varia- 

 tion in plant food, (3) proximity of other plants, that is, whether 

 crowded or not, (4) weather and climate. Dandelions growing in 

 dense high grass will grow tall; those growing in closely mowed 

 quarters blossom near the ground. Many variations occur in 

 nature which cannot be explained by any of these causes. 



Survival of the Like and Unlike. — Heredity is one of the most 

 important factors for the plant breeder to study. This is the law, 

 that all creatures inherit from their ancestors certain forms, char- 

 acteristics, and qualities. The law of heredity may be expressed 

 briefly by saying that "like produces like" and "similar produces 

 similar." 



Heredity, linked with natural variations are the two funda- 

 mental factors which when placed in the hands of the skilful 

 breeder will attain wonderful results. Varieties without end are 

 formed and yet these become so well established that the 

 grower can confidently depend upon their reproduction in garden, 

 orchard, or farm work. 

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