178 



THE AMERICAN NATURALIST 



[Vol. XLII 



This brings me to the statement of a principle of agri- 

 cultural cropping which, though generally recognized by 

 breeders for years, yet needs to be much emphasized by 

 those who would improve a character of a plant or a 

 plant strain, or maintain a standard of a general crop; 

 namely, the condition under which a character originated 

 or is being originated must be maintained or approached. 

 It is all the more important to hold this feature of crop- 

 ping well in mind, now that the conception of unit char- 

 acters and of mutations and of new methods of experi- 

 mental breeding has proved to be of such fertile aid 

 in the production of new types. Much of the value of 

 agricultural, commercial cropping rests upon the per- 

 manence and general use of a few well-maintained or 

 established varieties as against the miscellaneous use 

 of many varieties ; thus, for instance, a district or country 

 gains its reputation for a particular crop not by the use 

 of many varieties, as, for example, of wheat, or oranges, 

 but by the use of a few which by careful work are held 

 to their characteristic qualities. It is quite possible to 

 swamp agriculture by the creation of too many forms. 

 Stable industries are built up about reasonably stable 

 crops. 



After a new type or a new character in a type has been 

 obtained, new conditions, if they include the essentials 

 of the old conditions, may readily bring about the ad- 

 dition of new features whether we have in mind calling 

 these new features fluctuating or elementary. If the 

 originating conditions are lost or are not maintained, the 

 type should degenerate or retrograde, lose character, and 

 I am quite convinced that it always does. Herein lies 

 the working basis for every-day cropping and breeding. 

 This line of argument is equivalent to saying that so- 

 called fluctuating variations may be maintained and built 

 upon as foundations for important hereditary changes, 

 whether, in writing, we term the resultants mutants, 

 sports or simply elementary units or species. It is equiv- 

 alent to arguing that the principle of adaptation may 



