SOILS-PLACE IN ROTATION. 251 



would be likely to induce too luxuriant a growth of 

 stem, and to reduce the power of the plant to perfect 

 its seeds. In such soils, however, peas may be grown 

 advantageously mixed with beans the bean stem afford- 

 ing the necessary support to the pea, keeping it off the 

 ground, and giving it access to the air and the' sun, and 

 the mixed crop yielding a greater return than if beans 

 had alone been sown. This is a favourite practice in many 

 districts, as it is said not only to increase the yield, but 

 also to reduce the chances of loss from blight, which 

 appears to be less injurious in its attacks than when either 

 plant is sown alone the beans retaining their vigour 

 and producing a crop should the "green aphis" attack the 

 peas; while the peas remain uninjured when the "black 

 aphis" (p. 235) is destroying the beans. In many seasons 

 the entire crops of large districts have been destroyed by 

 the visitation of these insects. In 1854 the bean crop in 

 the south suffered severely from the " black aphis ;" and 

 in 1858 the pea crop throughout a wide range of country 

 was similarly injured by its green congener. In Scotland 

 peas are rarely sown by themselves : neither the soils nor 

 the climate are so suitable for their cultivation as in the 

 south. In some of the warmer districts, and on the rubbly 

 soils of the disintegrated trap rocks, too thin in many 

 cases for beans, peas are cultivated successfully, and give 

 very good returns. 



As has been before remarked, peas, in ordinary farming, 

 seldom enter into the regular rotations. Where they do, 

 they ought always to occupy that place which has been 

 assigned to beans, as a member of the leguminous order 

 of plants. This can be very well arranged, where it is 

 desired, as peas may be grown successfully on a class of 

 soils which are not the best suited for beans. On the light 

 soils farmed on the four-course system, it is very desirable 

 to alternate some other leguminous crop with the clover, so 



