130 FORAGE CROPS. 



mon field pea begins to show signs of trouble or dis- 

 tress, from the excessive heat, the cowpea begins to 

 flourish ; accordingly it would not be incorrect to say 

 that the southern isothermal for the common field 

 pea is the northern isothermal for the cowpea. Either 

 one of these plants, therefore, may be said to be the 

 complement of the other in the economy of our 

 agriculture. 



The cowpea is of very many varieties. These 

 are nearly all the product of the present century, 

 and the number is continually increasing. They 

 differ very much in their habits of growth. These 

 differences are such as relate, first, to the strength 

 of the vine and the amount of foliage and fruit 

 which it bears; second, to the character of the 

 growth, as erect, trailing or intermediate; third, to 

 the size, shape and color of the leaves, blossoms, 

 pods and peas, respectively ; and, fourth, to the time 

 of maturing. These differences cannot be dwelt 

 upon here. Among the favorite varieties in the 

 south are the Unknown, sometimes called Wonder- 

 ful, the Clay and the Whippoorwill or Speckled. 

 Among the favorite varieties in northerly latitudes 

 are the Whippoorwill and the Black. 



Distribution. — It has already been intimated 

 that the cowpea is a child of the sun, and that in con- 

 sequence it is not adapted to cool latitudes. In its 

 most perfect form it cannot at present be grown with 

 marked success east of the Mississippi and north of 

 forty degrees, that is to say, north of the cities of 

 Philadelphia, Columbus, Indianapolis and Spring- 

 field, in the states of Pennsylvania, Ohio, Indiana 

 and Illinois, respectively. West of the Mississippi 

 the line would run across the states of Iowa, 



