24 Plant-Breeding 



on a plant are alike ; and we are now able to understand 

 that sports or bud-varieties are no more inexplicable 

 than seed-varieties. 



What cultivation is. Cultivation is really but an ex- 

 tension or intensification of nature's methods of dealing 

 with the plant world. The ultimate result of both nature 

 and man is to supply more food. The variations which 

 arise from the effects of mere cultivation, therefore, are in 

 kind very like those which nature produces, the chief 

 differences being that of degree. The accustomed opera- 

 tions of the farmer, therefore, have been powerful agents 

 in the evolution of vegetable forms. The ways in which 

 cultivation affords a more liberal food supply are as 

 follows : 



1. By isolating the individual plant. The husbandman 

 sets each plant by itself, and then protects it by destroying 

 the weeds or plants which endeavor to crowd it out. 

 There is a partial exception to this in the " sowed crops," 

 like the grains, and it is noticeable that variation in these 

 plants is usually less marked than in the "hoed crops." 



2. By giving the plant the advantage of position, 

 whereby it is allowed the most congenial exposure to sun 

 and contour of land. 



3. By increasing the fertility of the land, either by tillage 

 or the direct application of plant-food, or both. Rich 

 and moist soils tend to "break" the type, or to cause 

 initial variations, to produce verdant colors and loss 

 of saccharine and pungent qualities, to induce redundant 

 growth, and to delay maturity and thereby to render 

 plants tender to cold winter climates. 



4. By thinning the tops of plants and the fruits, whereby 



