Long ago the view that this gas might be the source of the combined nitrogen found in different forms within the plant, was critically examined, particularly by Boussingault, and later by Lawes and Gilbert and by Pugh, and it was ascertained to be erroneous, the plants only taking nitrogen into their substance when it is presented to their roots in the form of nitrates of various metals, or compounds of ammonia.
In Canada and the United States this rational employment of a leguminous crop for ploughing in green is largely resorted to for the amelioration of worn-out wheat lands and other soils, the condition of which has been lowered to an unremunerative level by the repeated growth year after year of a cereal crop. The well-known paper of Lawes, Gilbert and Pugh (1861), " On the Sources of the Nitrogen of Vegetation,.
The late Dr Pugh took a prominent part in this inquiry.
Pugh), London (1805-1809); B.
Pugh], Walks through London (1817); London (edited by Charles Knight 1841-1844, reprinted 1851, revised by E.