APPLICATION OF SCIENCE TO PLANT CULTURE. 89 



plants or soil in ordinary culture during the period of growth, is 

 very large. The}' sa}' : " We would submit that the careful con- 

 sideration of the history of agriculture, both ancient and modern, 

 fails to afford evidence of compositions such as is now sought for. 

 Indeed, we would say, as we have done before that . . . the his- 

 tory of agriculture throughout the world, so far as it is known 

 clearly, shows that the fertile soil is one which has accumulated 

 within it the residue of ages of previous vegetation, and that it 

 becomes infertile as this residue is exhausted." 



As to the action of micro-organisms in providing nitrogen for 

 the plants, they regard it as very important, but are inclined to 

 limit it to the preparation of nitrogeneous materials already- in the 

 soil for the use of the plant, rather than the acquisition of nitrogen 

 from the air b}- either plant or soil. 



In the meeting of the German Association, last September, 

 Professor Hellriegel brought reports of a very extended series of 

 experiments in plant culture in continuation of those reported the 

 year before. The last number of " Die Landwirthschaftlichen 

 Versuchsstationen," contains a short account, which I translate. 

 The full details have, I believe, not yet appeared in print — at 

 least I have not seen them, though, of course, they are awaited 

 with no little interest. 



" The experiments were made with oats, buckwheat, rape, peas, 

 seradella,* and lupines. The plants were grown in a soil of pure 

 sand which had been shown by anah'sis to be entirely free from 

 nitrogen. In this sand, when the necessar\' mineral ingredients 

 had been added, all the plants continued growing until the}' had 

 used up the nitrogen of the seed and no longer. When, however, 

 a soil infusion was prepared by soaking a quantit}' of ordinary 

 soil in water, letting it settle and then taking off as much of the 

 solution as would correspond to one square inch of the surface 

 soil, and which contained from three-tenths to seven-tenths of a 

 milligram of nitrogen, and that amount of solution was put into a 

 pot containing eight pounds of sand, then the different plants 

 manifested a very different behavior. 



The oats, rape, and buckwheat were unaffected by the soil solu- 

 tion ; they remained in the condition of nitrogen starvation. But 



* Ornithopus sativus, an animal leguminous plant, native of Portugal. It is a val- 

 uable agricultural plant, producing an abundant crop of excellent fodder where 

 nothing else will grow to perfection. 



