320 CONTRIBUTIONS FEOM THE NATIONAL HERBARIUM. 



both sides of the Pacific, that the ethnological evidence afone might 

 not be sufficient, but the addition of definite botanical data may 

 yield conclusive proof. The earlier idea of an Asiatic origin of Amer- 

 ican civilizations having been given up, the tendency has been to 

 believe that agriculture and other arts of civilization have developed 

 quite independently on the two sides of the Pacific. But even if we 

 were willing to believe in closely parallel developments in customs 

 and arts, this could not explain the prehistoric distribution of the 

 same cultivated plants over the Tropics of both hemispheres. 



ORIGIN OF CULTIVATED VARIETIES OF THE COCONUT PALM. 



One of the most convincing arguments for the Malayan origin of 

 the coco palm was the existence of many and very diverse varieties 

 in the East Indies. It was a favorite line of reasoning with De 

 Candolle that the native home of a species was the region in which 

 it had been longest in domestication. The length of the period of 

 domestication was inferred from the number of varieties as a meas- 

 ure of the time that selection had been at work. Such calculations 

 were applied to the sugar cane, the taro, and numerous other plants. 



In dealing with the coco palm this plan seemed to be particularly 

 effective, for nearly all of the recorded varieties are in the East 

 Indies. The coco palm in America is not as uniform as commonly 

 supposed, though the varietal diversities do not approach those of 

 the Malay region. 



Careful consideration of the evolutionary argument will lead, how- 

 ever, to a conclusion directly opposite to that reached by De Candolle, 

 for the greatest and most definite variations of a cultivated plant are 

 much more likely to occur and be preserved outside its natural range, 

 where intermixture with the wild type of the species is prevented. 

 There are many reasons for believing that the abrupt and striking 

 "sports" that appear among our cultivated plants are not, in reality, 

 caused by selection, but are induced by new conditions and by the 

 state of inbreeding that generally accompanies domestication. 



The normal or wild type of a species is generally prepotent over 

 the varieties which have arisen in domestication, so that the "im- 

 proved" breed rapidly "deteriorates" when allowed to become 

 crossed with the wild stock. Darwin and many later experimenters 

 have proved, also, that when diverse breeds are crossed the offspring 

 are very often not intermediate between the breeds, but tend to 

 revert to the ancestral form. The breeders of high-grade varieties 

 look upon such mongrels as degenerate, but from the standpoint of the 

 evolutionist they may be said to be recovering from the injurious 

 results of inbreeding. It was noticed, for example, that in parts of 

 Guatemala, where the wild tropical papaw (Carica) is common, the 

 cultivated trees also have very small fruit. The tendency to such 



