SUPPLY OF NITROGEN. 21 



plant; that is, these elements of nutrition obtained from the 

 elements of water which the roots are constantly throwing to 

 the leaves, and from some of the retained ox3'gen in the 

 decomposition of the carbonic acid. 



Now, we come to the nitrogen, and, perhaps, in the whole 

 round of the elements of plant-nutrition, here is the only one 

 where there may be a diversity of opinion. Nitrogen in the 

 form of ammonia, nitrogen in the form of nitric acid, is 

 washed down to the soil by water, the nitrates formed in the 

 soil and carried in the water to the roots of the plants, and, 

 perhaps, — nay more, ^^robabl^, from the elemental nitrogen of 

 the air absorbed by the leaves, — perhaps in the form of car- 

 bonate of ammonia or the elemental nitrogen ; and thus the 

 plant is supplied with its element of plant-food, — nitrogen. 



If we turn now to the mineral elements of plant-nutrition, 

 these are obtained from the soil. Not the crude, coarse mate- 

 rial of the soil itself. The plant does not live on soil, as soil, 

 but the potash, the lime, the magnesia, the soda, the phos- 

 phoric acid, where acted on by certain natural agencies and 

 reduced to a soluble condition, are taken in soil-water and 

 carried by this root-action to the plant, and there distrib- 

 uted, almost — as fiir as physiological examination goes — as a 

 foreign, useless and not needed material; yet, as we know, 

 absolutely essential for the production of the plant. 



Thus, gentlemen, we agree in relation to what plant-nutri- 

 tion is, and we agree in relation to the manner in which the 

 plant obtains its food. 



Turning now to the other side, — to the practical men, to the 

 farmers who till the soil and grow the crops, — we tind that 

 during all these forty years or more, there has been no advance 

 in opinion or in belief, and no change among practical men in 

 relation to the subject of feeding plants, or plant-nutrition. 

 I mean the average farmer measures everything by barn-yard 

 manure as the type. He estimates everything by the pile, by 

 the bulk, by the quantity, by the cord, by the load, or by the 

 ton ; and to him it is utterly preposterous, it is enigmatical, 

 it is beyond all belief, when you tell him that two or three 

 hundred pounds of certain elements, placed within reach 

 of the plant, will produce a larger crop than many tons 

 of raw, crude, unchanged, undecomposed material, whether 



