MEADOW PLANTS 51 
the legumes have the power to add nitrogen to the soil 
by means of the root nodules and the nitrogen-fixing 
organisms contained therein. The choice of the legume 
for this purpose depends largely upon the secondary uses 
that can be made of the crop. It may be made into hay 
or may be cut green and used for soiling or for silage 
(Par. 76). In the timothy region, clover is a staple crop 
(Par. 46). In the South, where no perennial legume is 
adapted to the conditions prevailing over most of the 
region, annual legumes are used. It is true that alfalfa 
is grown with success in many parts of the South, such as 
_ the alluvial valleys of the Mississippi and Red Rivers, and 
the black soil of central Alabama, but even here an annual 
crop may be desired for the other purposes mentioned 
above. The commonest of the annual legumes in the 
South are the cowpea and velvet bean. In the North, 
the field pea is much used, and in middle regions vetch 
and crimson clover. 
64. The cowpea (Vigna sinensis (Torner) Savi.) is a 
trailing vine with trifoliate leaves and slender, bean-like 
pods. Some varieties are bushy and trail only slightly. 
The cowpea is the standard legume for the South. Its use 
has extended gradually northward until some varieties 
are now grown as far as Michigan. It is a warm-weather 
species and cannot be sown until the season is well 
advanced. In the South this limitation presents little 
difficulty, but in the North only quick-growing and more 
hardy varieties can be used. The hay from cowpea is 
excellent in quality, but, like all succulent forage, requires 
special care in harvesting and curing. It should be 
remembered that the feeding value of a legume like the 
cowpea is much greater than its fertilizing value. Hence 
the dual use of the crop, the greater part of the vines 
