PLANTS AND THE ATMOSPHERE. 425 



a grain), and to the third 16 centigrams (2.4688 of a grain) of nitrate of potapsa. 

 From the very first the three plants betrayed the difference in treatment to which 

 they had been subjected : the first languished and died, tlie second developed 

 itself, although stunted, but the third was remarkable for its healthy condition. 

 At maturity the second had taken from the soil 4 centigrams of nitrate of potassa, 

 and the third 8. But what was especially remarkable was, that, during its exis- 

 tence, the latter decomposed twice as much carbonic acid as the former. Thus 

 did the nitrogen perform the ofSce of stimulating the other functions, and of 

 giving to the subject which received it, or of taking away from that which was 

 deprived of it, the vitality, without which it would not act upon the atmosphere. 



Now, let it be observed that a plant contains more than half its weight of car- 

 bon, and only some thousandth parts of nitrogen. What purpose, then, in vege- 

 tation does this substante serve, being necessary to it, and yet introduced into it* 

 only in so small a quantity? M. Payen will inform us. According to this skilful 

 chemist, all vegetable organs originate in a nitrogeuous substance analogous to 

 fibrine, to which, little by little, are added the fibrous and cellulRr tissues which, 

 expanding, produce the whole plant. This fibrine is never destroyed, is formed 

 in all the organs of the plant, and must thus be the rudiment of all its parts which 

 could not be developed without it, and, consequently, without nitrogen which is 

 its essential basis. To recapitulate, plants are composed of carbon, water and an 

 excess of hydrogen ; they contain, besides, a fourth simple body, nitrogen, found in 

 a very small proportion, but the presence of which is necessary to life. The 

 atmosphere furnishes carbon abundantly ; water, that is to say oxygen and hydro- 

 gen, is contributed by rains ; nitrogen is required from the soil, and since it is 

 rarely to be found there it must be introduced in the form of manures; this is the 

 great business of the agriculturist, the largest, most unavoidable and most pro- 

 ductive of his outlays. 



In spite of the solid information which we possess upon the subject that occu- 

 pies us, we cannot but declare upon many points the inadequateness of our know- 

 ledge. One of the most inexplicable facts, and one that ought most to awaken 

 our curiosity and to demand our investigation, is the great physiological fact, the 

 discovery of which I have narrated. Chemists have admirably studied carbonic 

 acid ; they know all the properties it possesses, they are able to foresee all the re- 

 actions it occasions or undergoes under every condition in which they please to 

 place it; they are ignorant of none of the circumstances which give birth to or 

 destroy it. However, they have never seen it decomposing in a cold state, under 

 the influence of light, in the presence of any inorganic matter whatever, and what 

 they are unable to do, the smallest leaf exposed to the sun performs immediately 

 with a rapidity and an abundance that fill the naturalist with admiration. In 

 ten hours, an aquatic plant gives forth fifteen times its volume of oxygen : a single 

 leaf of the water-lily (i^'r. nhmfar) exhales 300 litres (a litre being 1-760 pint) 

 every summer, and M.. Boussingault, having poured into a vase, filled with vine 

 leaves, exposed to the sun, a current of carbonic acid, oUected at its exit only 

 -pure oxygen. Ah well ! we must just confess that this fact so common, so easily 



