912 EXPERIMENT STATION RECORD. 



decomposition of the carbohydrates furnishes ammonia, which is 

 assimilated by the micro-organisms and used in the formation of 

 tissne. It is not, therefore, simply the nitrogen which has recently 

 been drawn from the air which is utilized by plants. They assimilate 

 also the nitrogen derived from vegetable and animal remains. 



The work of Pasteur has shown that the action of micro-organisms is 

 necessary to the transformation of the complex organic substances of 

 the tissues of living plants into the simple forms which may be assimi- 

 lated by plants. Without these organisms life would be impossible, 

 as Pasteur himself has said, because the work of death would be incom- 

 plete. By their intervention the complex substances are burned, the 

 carbon passing into the form of carbon dioxicl, the hydrogen into water, 

 and the nitrogen into ammonia; and in these different forms the matter 

 is again carried into circulation. 



It often happens that vegetable matter remains for a long time in the 

 form of humus; bat even in this form it is utilized by plants. The 

 humus is constantly subjected to the oxidizing action of the lower 

 organisms and undergoes gradual decomposition. The ammonia pro- 

 duced by the decomposition of the humus is assimilated by plants as 

 well as the readily available product of oxidation, nitric acid. 



Schlocsing and Miintz 20 years ago showed that nitrates are formed 

 in the soil by the action of organisms. More recently Winogradsky 

 has demonstrated that the action of two different organisms are neces- 

 sary for the transformation of ammonia into nitrates — one converts 

 ammonia into nitrites and the other completes the oxidation, producing 

 nitrates. We thus see that micro organisms seize upon the nitrogen of 

 the air and convert it into organic compounds ; they convert vegetable 

 matter into humus, and then break down this humus, producing ammo- 

 nia and finally nitrates. At every step they perform a useful work, and 

 are valuable auxiliaries of agriculture. 



There are, however, other organisms which interfere with the work of 

 the beneficial kinds. Breal observed several years ago that there is an 

 aerobic organism which decomposes nitrates and sets elementary nitro- 

 gen free. This organism is abundant in vegetable debris, especially in 

 straw. It is also encountered in the excrement of domestic animals. 

 The extent to which the losses of nitrogen in arable soils is due to the 

 action of this denitrifying organism and the conditions most favorable 

 to its action are questions which require further investigation. 



THE DIFFERENT FORMS IN WHICH NITROGEN IS UTILIZED BY PLANTS. 



If we follow the example of Boussingault and plant a sunflower 

 seed in a sterile soil to which the necessary mineral matter and increas- 

 ing amounts of nitrates are added, or if we repeat the experiment of 

 Hellriegel and plant barley in well-washed sand to which sufficient 

 mineral matter and increasing amounts of calcium nitrate are added, 

 we will find that the crop produced increases with the amount of 



