28 AGRICULTURAL VARIETIES OF THE COWPEA, ETC. 



the Whippoorwill, which is the most important American variety, has 

 never been obtained from a foreign source. The Whippoorwil mark- 

 ing on foreign seeds occurs principally in Chinese varieties, though 

 such colored seeds have also been obtained from South Africa and 

 from India. The Chinese varieties resemble most closely the Ameri- 

 can Whippoorwill, but none of them are identical with it. One of 

 two explanations must, therefore, be true : Either (1) that the original 

 source of the Whippoorwill variety has not been found, or (2) that 

 it has originated in this country by hybridizing or otherwise. A simi- 

 lar line of argument might be applied to other varieties. On the 

 other hand, in the collections of seed from abroad varieties indis- 

 tinguishable from some American varieties with black or black-eyed 

 seeds have been obtained, and from places which in all probability 

 had not obtained the seed previously from America. 



It is an interesting fact that most of the cowpeas imported from 

 China, as well as many from India and from Africa, are very much 

 subject to bean rust ( Uromyces phaseoli) . American varieties, on the 

 other hand, are apparently wholly immune to this disease. Mr. W. A. 

 Orton makes the interesting suggestion that this points to this fungus 

 being an American native, and that by natural selection the American 

 varieties may have become immune to this disease in the same way 

 that the Iron cowpea has become immune to wilt and to root-knot. 



In regard to the seed colors of the numerous varieties of cowpeas, 

 practically every color represented in American varieties of cowpeas 

 has been obtained from abroad, so that so far as this point is con- 

 cerned all of the American varieties may have been introductions 

 from foreign countries; but plenty of evidence exists that many of 

 the American varieties have originated by natural hybridizing in 

 this country. Over the greater part of the region where the cowpea 

 is grown, natural hybrids are of very infrequent occurrence. Never- 

 theless, a new kind of seed as regards coloration would easily attract 

 one's attention and there can be little doubt that many of the Ameri- 

 can varieties have thus originated as chance hybrids. In at least 

 two localities in the country, as hereafter explained, cowpea hybrids 

 occur in great numbers, so that there is no difficulty in accounting for 

 the numerous American varieties in this way alone, especially when 

 we remember that several varieties were introduced as early as the 

 beginning of the eighteenth century. 



SIMILARITY m HABIT OF VARIETIES FROM THE SAME SOURCE. 



One of the rather startling results of testing cowpeas derived from 

 the same foreign source is that the varieties often turned out to be 

 extremely similar in habit and appearance notwithstanding the fact 

 that the seeds were very different. Thus in a series obtained from 



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