CAIN: CENTER OF ORIGIN 143 



merits concerning size and favorableness of environment are generally correct, 

 but there is no necessary relationship between size and center of origin or 

 center of distribution. It would seem that geographic trends in adaptive charac- 

 ters are usually nothing more than the dines of Huxley (1940). Allen's state- 

 ments were questioned by Cockerell (1906) who said, "I found in that genus 

 {Hymenoxys chrysanthemoides) a case which seemed to me to exactly agree 

 with those postulated by Dr. Allen, except that the large form was southern, 

 the small one northern." To take another case, it is a common observation 

 among botanists that plants on oceanic islands, such as the Azores, Canaries, 

 and the Galapagos, are frequently of larger stature than their relatives on the 

 mainlands from which they were derived. This larger size of herbs, shrubs, and 

 trees would seem to be related to the long growing season, rather than to any 

 hypothetical indication of their island origin. 



I have tried to find an authentic case among plants either in favor of the 

 criterion or opposed to it in which the data are adequate, but have failed to do 

 so. The following notes are only suggestive. Prosopis, for example, attains its 

 largest size (height of about 50 ft.) in the Rio Grande valley, where the genus 

 is near its periphery. Shreve (1936) says, "It is only in the most favorable 

 situations that the mesquite is found as a tree. In less favorable ones it is merely 

 a shrub." The genus, however, is taxonomically complicated (Benson, 1941) 

 and has had a long and obscure history as indicated by its split range, being in 

 the South American deserts as well as in Mexico and our Southwest. It is 

 therefore impossible to be very certain concerning the history of its area. The. 

 Southern Appalachians are becoming famous for their large trees as the region 

 is better known. The largest single specimens known of Picea rubens, Tsitga 

 canadensis, Aesculus octandra, Tulipastrum acuminatum, and several others, 

 are found localized in the Great Smoky Mountains, but there is no evidence to 

 indicate the origin of these species in that region. 



One situation in which the tendency is opposite to the criterion has been 

 shown by cytology. Autotetraploids, and sometimes allotetraploids, are larger 

 than their progenitor diploids. Furthermore, they have a strong tendency to 

 extend the range of the group and to occupy peripheral positions relative to 

 the diploids. (Anderson and Sax, 1936; Babcock and Stebbins, 1938.) 



Criterion 5. Location of Greatest Productiveness and its Relative 



Stability in Crops 



From Adams' comments, it appears that he considers productiveness to be 

 closely related to size and numbers, and essentially a matter of growth and re- 

 production. According to Adams, Hyde (1898) concluded that crop produc- 

 tion, whether it averages high or low, will tend to be more uniform from year 



