ORIGIN AND FORMATION OF ORGANIC MATTER IN PLANTS. 915 



FORMATION OF NITROGENOUS MATTER. 



This is a subject of which little is known. A study of the changes 

 which take place in the atmosphere surrounding a plant shows that the 

 ratio of carbon dioxid absorbed to oxygen evolved is much less than 

 unity. Since in a study of assimilation in a detached leaf Boussingault 

 found this ratio to be equal to unity it is natural to attribute the larger 

 part of the excess of oxygen thus found to reduction of nitrates; for if 

 the chlorophyll cell is capable under the influence of sunlight of reduc- 

 ing so stable a compound as carbon dioxid it is fair to assume that it 

 could more easily reduce nitric acid. It is probable that the nitric acid 

 is transformed into ammonia which unites with carbohydrates to form 

 amids, which by successive steps are transformed into the complex 

 albuminoids. This, however, is simply an hypothesis which is not based 

 upon exact observation. 



CONCLUSIONS. 



When Priestley in 1771 made the discovery that plants purify an 

 atmosphere which has been vitiated by the respiration of animals he 

 proclaimed the solidarity of two kingdoms, an idea which gradually 

 took definite shape. 



Plants, agents both of reduction and of synthesis, decompose the 

 carbon dioxid of the air under the influence of sunlight and elaborate 

 organic matter, while the animal burns this organic matter and exhales 

 the carbon dioxid which nourishes the plant. The plant stores up in 

 its reserve materials the energy drawn from the sun and the auimal 

 consumes these materials, converting the energy into heat and work. 



Our views regarding this subject were broadened by the investiga- 

 tions of Pasteur, who demonstrated that the innumerable plants with- 

 out chlorophyll as well as the micro-organisms which swarm in the soil 

 are, like animals, destroyers of organic matter and producers of carbon 

 dioxid. Indeed, it seemed at first that their role was simply to "com- 

 plete the work of death," reducing the organic matter to those simple 

 forms which can be utilized by plants. One of their most important 

 functions, however, was ignored until Berthelot showed that these 

 organisms are not only agents of reduction, but that some of them are 

 agents of synthesis which draw into the cycle of life the most refrac- 

 tive of elements — nitrogen — while others have the power of fixing the 

 free nitrogen of the air. The solidarity of living beings thus appears 

 under another form. The fixers of nitrogen live and work only to 

 destroy the organic matter elaborated by the fixers of carbon — the 

 chlorophyll plants. 



If the tree holds sway on the plains, proudly spreading its branches; 

 if the valleys are covered with bright colored herbage; if the reaper 

 gathers the golden sheaves, it is due to the humble workers hidden in 

 the depths of the soil, one class fixing the nitrogen in complex combi- 

 nations, and others takiug up this matter, simplifying it, and convert- 



