DISTINCTIVE CHARACTERS OF COWPEA VARIETIES. 21 



to define are the size of leaves, varying from small to very large; 

 color, ranging from very pale to very dark; and number, varying 

 from few to very numerous, the number being correlated with the 

 length of the internodes. Such characters are of definitive value 

 only when approaching one extreme or the other. In a few cases 

 closely related varieties may be distinguished by the leaf surface ; for 

 example, Iron has nearly plane leaves, while most other buff -seeded 

 varieties have leaves decidedly undulate. 



FLOWERS. 



The flower of the cowpea occurs principally in two colors : White, 

 or nearly white, and pale violet or purple, in each case the eye being 

 yellow. The violet color merges by almost insensible degrees to the 

 white. The back of the standard is paler and often yellowish in the 

 white flowers or greenish in the violet. White flowers are mainly 

 associated with white or partly white seeds. The violet-flowered 

 sorts are far more numerous. 



SEEDS. 



Seeds of cowpea varieties differ in color, shape, and size. These 

 seed characters are by far the most useful by which to distinguish 

 varieties. Unfortunately, however, there are many examples of per- 

 fectly distinct varieties whose seeds are indistinguishable. On the 

 other hand some varieties are distinguishable only by the seeds. 



Color. — The seeds of all three species of Vigna have practically the 

 same range of colors. These may be classified into two groups, (1) 

 those in which the coloration is not uniform over the whole seed and 

 (2) those in which the color or pattern is uniform. 



Seeds whose color or color pattern is not distributed over the whole 

 surface exhibit four types of variation : 



(1) Spotted, with round or roundish spots. 



(2) Marbled, with spots elongate and running together, as in Whippoorwill. 



(3) Speckled with minute dots; as, for example, in Taylor and New Era. 



(4) Marbled and speckled; as, for example, in Groit. 



The commonest type has the second color concentrated about the 

 hilum, as in Blackeye, Browneye, etc. The term hilum as here used 

 refers to the scar at the place where the seed was attached to the pod. 

 It is always nearest the chalazal end of the seed and is lanceolate in out- 

 line, the broad end being next to the micropyle. The hilum is always 

 whitish in color, excepting its sides, which are nearly always dark 

 olive. In most cowpeas the raised circle about the hilum is different 

 in color from the body of the seed, in which case it is referred to as 

 the iris. This "eye spot" varies in different varieties from small 

 (in seeds designated "eyed") to very large (in "saddled" seeds). 



229 



