538 STRUCTURE AND LIFE HISTORIES 
biological world with a new method of study. It has 
demonstrated that the method of evolution may be studied 
by experimentation, and this demonstration is, probably, 
de Vries's greatest service to science. The mutation 
theory should also be of great service to breeders. It 
has helped to establish plant and animal breeding on a 
more scientific basis, has pointed the way to correct 
methods where men were formerly groping in the dark, 
and has showed that results of commercial value do not 
require a life time, but may be obtained within two or 
three seasons. By the application of modern methods it 
has been possible, within a few seasons, to obtain new 
strains of oats yielding as much as 14 bushels per acre 
more than the variety from which they were derived, and 
to produce new strains of corn not only giving a larger 
yield, but maturing nearly two weeks earlier than the 
parent variety. 
459. Classification. Mere information is not science. 
A "book of facts" is not a scientific treatise, for it is 
composed of bits of unrelated information, presented on 
some artificial basis of sequence, as for example, alpha- 
betically. Scientific knowledge, in addition to being as 
accurate as possible, is characterized by having an orderly 
arrangement in one's mind, and this order is based on a 
logical, fundamental relationship between the facts and 
ideas. Only by such an arrangement of our ideas are we 
able to understand their relation to each other, their rela- 
tive importance, and their real significance. Classifica- 
tion, therefore, is essential to all science. The very 
existence and use of such words as oaks, maples, roses, 
indicate that men have grouped or classified their ideas 
of certain plants (e.g., red oaks, white oaks, black oaks, 
