ELEMENTARY SPECIES IN AGRICULTURE. 



Franklin's name is honored all over the world, and the splendid 

 services he has rendered to science and to humanity have had their 

 influence in Europe as they have in America. Your president and 

 secretary, in inviting me in your name to attend this celebration of 

 the bicentennial of your great founder's birth, have offered me a 

 welcome occasion of paying a tribute to his memory. It is not, how- 

 ever, without hesitation that I have accepted this honorable invita- 

 tion. Philadelphia has been the center of botanical interest and 

 research in this country for more than a century. The various con- 

 tributions of your society to biological science are followed in Europe 

 with intense interest. To speak before such a famous sphere of 

 learning is not only a high honor, but also imposes a great obligation. 

 In accepting the invitation I have trusted to your indulgence and to 

 the interest shown by you in the broad questions of evolution, which 

 of late have returned to the empirical methods and principles laid 

 down by Darwin. 



New facts and new conceptions are the result of half a century 

 of industrious work. Darwin relied for a large part on the methods of 

 selection which at his time were in use both in agriculture and in 

 horticulture. He tried to show that the evolution of species at large 

 has followed the same laws that underlie the evolution of races and 

 varieties in culture. In broad lines he has succeeded in convincing 

 his contemporaries of the validity of this analogy. Agricultural and 

 horticultural experience, however, were at his time only imperfectly 

 developed, and the amelioration of races, though successful in a large 

 number of cases, had no really scientific basis. It did not afford all 

 the evidence required for a thoroughly reliable theory. Complying 

 with the prevailing belief of the most renowned agriculturists, which 

 considered the breeding of races as a slow process of gradual 

 amelioration, he proposed the same slow and almost imperceptible 

 changes as the source of evolution in nature. Since his time experi- 

 ence and theory have made very manifest advances. Especially 

 the principle of the unit-characters, which is the basis of the theory 

 of origin of species by mutation, leads us to the acceptation of salta- 

 tory changes or so-called sports as the most probable way of nature 



