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 
(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 Macmillan Co., New York. 
