310 ESSENTIALS OF BOTANY 



wheat-field will show many varieties, some better, others 

 poorer than the average wheat plant of the field. 



Timothy is the most valuable grass for hay in the 

 majority of the northern states. Some of its most impor- 

 tant variations concern such points as these : ^ 



(1) Duration, whether annual or perennial. 



(2) Power to spread by branches from the base of 

 the stem (stolons), some plants producing 10, others 250 

 heads. 



(3) Relation of seed-production to leaf-production : some 

 plants leafy and making good pasture, but bearing little seed. 



(4) Yield : single plants sometimes produce less than | 

 pound of hay and others over 1| pounds, or more than five 

 times as much. 



390. Selection of Parent Plants. — For thousands of 

 years farmers and gardeners knew of no better way to 

 secure good seed than to save that which was produced by 

 the most promising accidental varieties. But during the 

 nineteenth century growers of several kinds of crops, 

 especially wheat and sugar-beets, hit upon a more com- 

 plicated and successful plan. Seed from a good many of 

 the most promising plants in a field is saved. This seed 

 is then sown in isolated ground, and the plants raised from 

 it are carefully tended to serve as parents for a new gener- 

 ation of improved plants (Sect. 394). This process carried 

 through several generations, with careful attention paid to 

 the number and characteristics of all the descendants of each 

 original parent, furnishes a sure means of improving the 

 race of plants thus treated. 



391. Results of Breeding by Selection. — Already vol- 

 umes have been written describing some of the most im- 



1 See Bailey's Plant Breeding, Chapter V, The MacmiUan Co., New York. 



