SOYBEANS 517 



known. The hairiness occurs in two colors, grayish and 

 tawny. The tawny pubescence is nearly always associated 

 with dark-colored pods and usually with purple flowers. 

 The leaves of the soybean show large variation in size, 

 shape and color. The leaflets are usually ovate-lanceo- 

 late, but in some varieties are narrowly lanceolate or 

 almost linear. In broad-leaved varieties they may be 

 nearly orbicular. With few exceptions the leaves of the 

 soybeans begin to turn yellow as the pods ripen and usually 

 all have fallen by the time the pods are mature. In a few 

 sorts, however, the leaves persist and retain their green 

 color even after all of the pods have ripened. 



629. Soil adaptations. Soybeans are not particular 

 in their soil requirements. Even on poor soil they will 

 make a satisfactory growth, provided they are inoculated, 

 but on such soils the growth is rarely as good as is made 

 by cowpeas. They succeed best on loams and clays, but 

 the Mammoth variety also does admirably on sandy or 

 silty soils. They are not sensitive to an excess of moisture, 



. although they will not thrive in a soil where water stands 

 for any considerable length of time. In marked contrast 

 to their ability to grow on wet soils is the fact that the 

 soybean is also decidedly drought resistant, much more 

 so than cowpeas. Unfortunately, however, rabbits are 

 very fond of the soybean, and in the semi-arid regions the 

 danger of damage from these animals is a serious dis- 

 advantage. 



630. Climatic adaptations. In the United States, soy- 

 beans show almost exactly the same range of climatic 

 adaptation as varieties of corn. Early varieties will 

 mature northward wherever corn will mature. South- 

 ward, however, the soybean does not seem to be adapted 

 to as extreme climatic conditions as the corn ; for example, 



