152 The Rothamsted Grass Experiments. 



in the leguminous herbage only 4'21b. without, but 18'21b 

 with, the manure, or 14'01b. more with it than without it. 



The much- debated question as to the source of this 

 increased nitrogen of the leguminous herbage is here 

 answered in favour of the soil, and, in the case of clover and 

 beans at any rate, more probably the lower than the upper 

 layers. In the unmanured herbage the deeper-rooting Lotus 

 corniculatus (lesser bird's-foot trefoil) and Trifolium pratense 

 (meadow clover) contributed most of the leguminous produce ; 

 but in the manured herbage it is the comparatively surface- 

 rooting Lathyrus pratensis (meadow vetchling) that mainly 

 contributes the leguminous increase. 



The agricultural importance of the mode of root-distribu- 

 tion is further illustrated by gramineous plants. Spring- 

 sown barley, which has but a short time in which to extend 

 its roots, and to gain command of the resources of the soil, 

 throws out a large quantity of fibres near the surface, and is 

 more benefited by the action of direct mineral manures than 

 is the autumn-sown wheat, which has four or five months 

 longer for root-distribution, and is less dependent on the 

 stores of the surface soil. Accordingly, the greatly increased 

 gramineous yield in the mixed herbage by the purely mineral 

 manure was almost exclusively due to the much denser 

 growth, and much greater tendency to form stem and seed, of 

 the creeping and surface-rooting Festuca ovina (sheep's 

 fescue), Agrostis vulgaris (fine bent), and Holcus lanatus 

 (Yorkshire fog). 



How far is the increased growth of the grasses proper in 

 the mixed herbage arising from an increased accumulation of 

 combined nitrogen available to them in the upper layers of 

 the soil the result of the increased growth of, and accumula- 

 tion by, the Leguminosse induced by the mineral manure? 

 In other words, is there, where the plants are thus growing 

 in association, a parallel action to that which takes place 

 when they are grown in alternation (as wheat after clover, 

 the clover crop having left the upper layers of the soil rich in 



