432 PLANTS AND THEIR RELATION TO MAN 



ditions and develop into fine plants, crowding out the weaker 

 ones that have developed from poor seed. The survival of 

 strong, hardy plants is known as the survival of the fittest. 



Selecting seeds. Good plants come from good seeds, and 

 if we wish hardy, healthy, crop-bearing plants, we must sow 

 seeds which have come from strong, vigorous plants. If seeds 

 are yearly selected from plants which yield the best and largest 

 crop, there will be a steady improvement in the size and quality 

 of the harvest, and a distinct gain to the grower (Fig. 299). 



FIG. 299. Good clover seed. Poor clover seed. 



By careful selection of seed we are able not only to improve 

 the quality and quantity of the crop, but also to secure other 

 results of commercial value. The peas which are earliest in 

 the market bring higher prices than those which come later in 

 the season, and hence growers make strenuous attempts to 

 obtain early peas. They sow seeds from the plants which 

 ripened peas the earliest, and by following this practice year 

 after year, they finally obtain plants which grow in colder 

 weather and ripen their fruit much earlier than the average. 



The fibers of the stem of the flax plant are woven into linen 

 materials and the longest fibers are of the greatest commercial 

 value. In order to increase the height of the stem and the 

 length of the fibers running through it, seeds are picked only 

 from the plants having the longest stems. As a result of careful 





