568 STRUCTURE AND LIFE HISTORIES 
gence with which we may order our own conduct and lives. 
If the study of plants had rendered no other service to 
mankind than this contribution of an effective method of 
ascertaining the laws of heredity, it would have amply 
justified all the arduous labor that men have devoted to 
it for 2,000 years. 1 
1 Only one of the simplest cases worked out by Mendel is summarized 
in this chapter. A more thorough study of his experimental results and 
theories must be reserved for a more advanced course. 
