4S8 BOTANY OF CROP PLANTS 



purposes by bakers, confectioners and chocolate manufac- 

 turers. The seeds of soy beans are sometimes used as a 

 substitute for coffee. Soy-bean hay has a comparatively 

 high feeding value. It is recommended as a pasture for 

 hogs. The plant is recognized as a valuable soiHng and 

 ensilage crop. Nitrogen-fixing bacterial nodules occur on 

 the roots of the soy bean. 



VIGNA (Cowpea and Related Species) 



Description. — The "Vignas" are usually climbing or 

 trailing herbs, sometimes erect, that are much like the com- 

 mon bean. They differ from the common 1^ean {Phaseolus 

 vulgaris), however, mainly in that the keel of the corolla is 

 short and merely incurved rather than spirally coiled. The 

 leaves are pinnately trifohate. The flowers are yellowish or 

 purpHsh, in head-shaped or racemose inflorescences at the 

 ends of long pedmicles; these arise in the axils of leaves. 

 The calyx is five-toothed. The stamens are diadelphous 

 (nine and one). The ovary is sessile, many-ovuled, and 

 bears a style that is bearded along the inner side. The 

 pods are linear, straight or slightly curved, and two-valved. 

 The seeds are much like the common kidney bean in shape 

 (Fig. 193). 



All the Vigna spp. (''Vignas") are natives of warm and 

 tropical regions, and consequently they have been most 

 successfully cultivated in the Southern States. 



Species. — There are but three cultivated species of 

 "Vignas": Vigna sesquipedalis (asparagus bean), Vigna 

 catjang (catjang), and Vigna sinensis (cowpea). The as- 

 paragus bean has pendant pods i to 3 feet long, and kidney- 



FiG. 193. — Seeds of i6 varieties of Vigna showing range in variation of 

 shape, size and color. The top three rows are catjangs (Vigna catjang), the 

 bottom two rows are asparagus beans (Vigna sesquipedalis), and the others are 

 cowpeas (Vigna sinensis). (,After Piper, U. S. Dept. of Agri.) 



