PRACTICAL ItfFEREKCES. 121 



periments, although not in the manner that might at 

 first have been supposed. Leguminous plants, such as 

 clover, beans, vetches, though containing so much nitro- 

 gen in their composition, are not only not specially bene- 

 fited by nitrogenous manures, but they absolutely leave 

 the land richer in nitrogen than it was before (Lawes 

 and Gilbert), and thus prepare it for the growth of grain 

 crops, which, though chiefly starch -producing, 'are yet 

 specially benefited by nitrogenous manures. 



In growing beans and wheat alternately at Kotham- 

 sted, it was found that eight crops of wheat grown al- 

 ternately with beans supplied nearly as much produce 

 (grain), and nearly as much nitrogen in that produce as 

 were furnished by sixteen crops of wheat grown without 

 manure. Here, then, the manure supplied to the beans 

 not only favored those plants, but left a residue in an 

 available form for the wheat. 



Botanically, the good effects of rotation are dependent 

 on the variations in the mode of growth and in the in- 

 ternal structure of roots, which allow of different layers 

 of soil being utilized for plant-food, while the specially 

 different requirements of different classes of plants obvi- 

 ate the exhaustion of any one ingredient, and give time 

 for the accumulation of fresh supplies. 



Improvement of Cultivated Plants. This has already 

 been alluded to, but its importance justifies repetition, 

 the more so as to a considerable extent it is a matter that 

 the farmer can do for himself. A series of small experi- 

 mental plots might well be instituted on every farm. 

 The first and perhaps most general use to which such 

 trial grounds should be put, would be to test the quality 

 of purchased seed, and ascertain what proportion might 

 be expected to grow under different conditions. Other 

 experiments should be devoted to the purpose of ascer- 

 taining what particular varieties are likely to do best in 

 6 



