B. P. I. — 69.3. 



AGRICULTURAL VARIETIES OF THE COWPEA AND 

 IMMEDIATELY RELATED SPECIES. 



THE CULTIVATED SPECIES OF VIGNA. 



The botanical genus Vigna, to which the cowpea belongs, is closely 

 related to Phaseolus, which includes the common kidney bean. The 

 chief diagnostic distinction is that the keel is only slightly curved 

 in Vigna and is twisted or spirally coiled in Phaseolus. Vigna has 

 also been much confused with Dolichos, which has a keel similar 

 to Vigna but has a terminal stigma, while in Vigna the stigma is 

 lateral. Botanical works contain descriptions of about 60 species 

 of Vigna. Omitting the three cultivated species hereafter mentioned, 

 according to Mr. W. F. Wight, these species are distributed as 

 follows: Africa, 40; Madagascar, 2; Asia, 5; Java, 2; Australia, 2; 

 Hawaiian Islands, 2; South America, 1; and cosmopolitan, 3. 



Most of the species of Vigna are annual, but some are perennial. 

 Several are more or less woody. Judging from descriptions alone, 

 very few of the noncultivated species seem to possess any characters 

 that would be desirable for the plant breeder. Thus far, none of 

 the wild species have been grown excepting the common Vigna 

 luteola (Jacq.) Benth. (V. glabra Savi), cosmopolitan in subtropic 

 regions, and V. vexillata (L.) Benth., obtained from Matanzas, Cuba. 

 The latter has the keel somewhat curved and bearing a lateral horn 

 very like that of Phaseolus calcaratus. It would therefore seem that 

 the original reference by Linnaeus of the plant to Phaseolus is 

 correct. 



The cultivated species are three, namely, the asparagus bean, Vigna 

 sesquij?edalis (L.) W. F. Wight ; the catjang, Vigna catjang (Burm.) 

 Walp. ; and the cowpea, Vigna unguiculata (L.) Walp. The differ- 

 ences in the botanical characters by which these species are distin- 

 guished are comparatively slight (Pis. I, II, and III) and, further- 

 more, the species are connected through intermediate varieties. 

 Whether we consider that all the varieties are referable to one 

 botanical species or to more is of little practical importance. All 

 three of them can be readily hybridized, as proved by the work of 



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