CHAPTER XVI 
SYSTEMATIC IMPROVEMENT OF PLANTS 
Improvement by selection . Crossing to produce new varieties - Application 
of Mendel’s law in crossing - Separation of the desired character - Behavior 
of the recessive - Behavior of the dominant - When more than two characters 
are involved - Systems of planting - Records 
The whole question of practical methods of plant improve- 
ment rests on an entirely different basis than that of animals. 
The evolutionary principles involved are identical, but the eco- 
nomic conditions are different, indeed almost opposite. 
Animals are relatively few in number and costly both in breed- 
ing and in maintenance. Plants, on the other hand, are cheap, 
and the numbers may easily run into the thousands, all of which 
warrants methods in plant improvement that would be entirely 
“impracticable with animals. 
Improvement by selection. Plants, like animals, are subject 
to improvement by the ordinary methods of selection ; indeed, 
much improvement is effected in that way. Farmers keep up 
the quality of corn by selecting for seed the occasional superior 
ear. The best wheat is chosen for seed and carefully screened 
of inferior kernels. In this general way we are constantly 
practicing selection. 
A new method of increasing yield of corn consists in planting 
selected ears, each in separate rows, carefully harvesting each 
row separately. Though the ears may have looked identical, the 
crop will vary greatly. That from some ears will be nearly uniform 
as to size and character of ear, while that from others will be 
exceedingly uneven, with many nubbins and inferior ears. The 
yield, too, will vary greatly, often running more than two to one 
in favor of certain ears, though they bore no visible indication 
198 
