PLANT BKEEDING 



259 



specimens. This work of improving plants by inducing them 

 to attain the highest development possible is called plant 

 breeding. 



Basis for breeding. The work of plant breeding is made 

 possible by the fact that all plants tend to vary within certain 

 limits. There is probably no species that is absolutely fixed as 

 to type, though some vary more than others. Even in the 

 plants which present the least amount of variation, nobody 

 ever saw two plants or even two leaves that were exactly 

 alike. Usually the plants that vary most 

 come from families that contain great num- 

 bers of species ; in fact, the species them- 

 selves may be looked upon as illustrations 

 of greater variations from the original stock 

 which have been developed through ages of 

 natural selection. Every one is so familiar 

 with the slight variations that occur in all 

 plants that they seldom occasion remark. 

 In any large area devoted to a single species 

 we expect to find the tall and the short, the 

 branched and the unbranched, the smooth 

 and the hairy, the pale and the more deeply 

 colored, the vigorous and the sickly, the 

 drought-resistant and the less hardy. It is 

 only when variation is manifested in the plant parts with which 

 we are especially concerned, such as the size and color of the 

 flowers or the abundance, size, and flavor of the fruits, that 

 we notice it and endeavor to make these favorable variations 

 permanent. That they can be made permanent, or even in- 

 creased in value, is shown by the superior plants everywhere 

 seen in cultivation. Strongly marked variations are usually 

 apparent in the seedlings soon after they have started into 

 growth, but others may not appear until the species has 

 reached maturity. The point of departure for most plant 



FIG. 188. A gera- 

 nium sport, show- 

 ing one truss of 

 flowers growing out 

 of another 



