PLANT BEBEDESTG 



413 



the plant. In the case of timothy, our most valuable grass for 

 hay, the important 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 httle seed. 



(4) Yield, — single plants sometimes producing less than 

 ^ pound of hay and others 

 over 1^ pounds, or more 

 than five times as much. 



379. " Coming true from 

 the seed." Only careful 

 trials can settle the ques- 

 tion whether in any given 

 case (as in that of timothy) 

 variations from the usual 

 type will be fully trans- 

 mitted from the seeds of a 

 plant to the offspring, or, 

 as farmers and gardeners 

 say, will " come true." But 

 there is enough chance of 

 success to make it worth 

 while to try to perpetuate any promising new plant or variation. 

 The reason why cultivated plants show such improvement 

 over their wild originals (Fig. 331) is, in the case of those 

 grown from seed, because desirable modifications in these 

 plants have occurred, and the seed of the improved individuals 

 has been saved and has transmitted the improved characteristics 

 to new generations. 



380. Variation in wheat. Wheat has been cultivated in 

 China for not less than 4600 years, and for thousands of years 

 many varieties have been grown throughout the vast tem- 

 perate region from China to western Europe. It is thought 



1 See Bailey, Plant Breeding. The Macmillan Company, New York. 



Fig. 331. Increase in size of the potato 

 tuber due to cultivation 



The upper tuher is a wild one, the lower 



a small cultivated tuber ol the Vermont 



variety. Each one half natural size. Wild 



potato after J. Sahine 



