390 cook 



For the practical breeder, as for the scientific investigator, 

 nothing should be taken for granted until verified by actual ex- 

 periment, but it is, nevertheless, useful to have, if possible, a 

 system of interpretation by which results once attained can be 

 understood, and proper discrimination made between the rela- 

 tive prosoects of alternative fields of investigation. Selections, 

 mutations, crosses and hybrids, have entirely different impor- 

 tance in different groups, depending upon the nature of the 

 characters which it is desired to secure, and upon the adapta- 

 bility of the species to different methods of propagation. In the 

 amelioration of coffee, for example, mutations promise little be- 

 cause of their smaller production of seeds, but if the flowers or 

 pulp of the berries were the valuable part, mutations would be 

 as valuable as among other horticultural species. 



Selection and hybridization have been thought of as two alter- 

 native methods by which evolution might be brought about, and 

 the debate has continued as to which is the better. The question 

 could never be answered in this form, for the assumption on 

 which it is asked is a false one. The normal species, the unit 

 of evolution, is neither stationary nor uniform. It not only 

 makes a slow and gradual advance, as a whole, but it manifests 

 all the time a vast diversity among the different individuals. 

 Some of this diversity is induced by the environment, but much 

 of it is quite spontaneous and continues to appear even in a 

 uniform environment. 



The value of selection does not lie in any power to cause 

 these inherent differences ; it can only preserve them and pre- 

 vent, as it were, the swinging back of the pendulum of normal 

 diversity. The alert breeder seeks to catch it at its highest and 

 to hold it steadily there. It cannot be held forever, as is now 

 generally recognized. Sooner or later the selected type deterio- 

 rates, and shows itself inferior to some more recent selection 

 which has lost less of the normal vigor of the species. 



To hybridize selected varieties may serve merely to release 

 the pendulum and allow it to swing back along the curve of 

 normal diversity. The vast majority of the progeny are likely 

 to be inferior to the parents in the special qualities which have 

 made them valuable. Some of them may approach the standard, 



