XXVI. IMPROVEMENT OF PLANTS 



Origin of Domestic Plants. Many of our common cultivated 

 plants have been so changed and improved under the care of man 

 that we can scarcely realize that they originated from wild inferior 

 plants. The potato is not a native of Ireland, as many people 

 suppose, but its home is in some of the high valleys of the Andes 

 Mountains; and travelers passing through South America may 

 often see Indians selling these wild potatoes in the streets of Peru- 

 vian and Bolivian cities. Many of these wild varieties are no 

 larger than a common marble and have such a strong, disagreeable 

 flavor that most of us would not care to eat them at all. The 

 chrysanthemum was once regarded as a pestiferous weed, and the 

 tomato at one time was grown simply as an ornamental plant and 

 its fruit was regarded as poisonous. From the insignificant 

 European crab apple many , of the fine varieties of apple trees 

 have been derived. Strawberries and blackberries afford striking 

 illustrations of what changes may be brought about by careful 

 cultivation, since the wild varieties of both plants are quite 

 common in many parts of our country, and may be easily compared 

 with the cultivated varieties. . As we note the differences in the 

 wild varieties and the cultivated varieties of the same plant, the 

 question naturally arises by what means has the improvement of 

 the plant been brought about. In reply we can say that all plant 

 improvement depends on three factors: (1) variation, (2) heredity, 

 (3) selection. 



Variation. This is the first requisite toward the improvement 

 of plants and is the chief means through which progress is pos- 

 sible. By variation we mean the tendency of the plant to be un- 

 like its parent. If we go out into a field of corn, we shall not find 

 any two plants that are alike in all respects. One plant will have 

 a tall stalk, another a thick, heavy stalk; one will have a large 

 number of small, short ears, while another will have a few long, large 

 ears. One ear will have heavy thick grains of a light color, while 



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