426 PLANTS AND THE ATMOSPHERE. 



accomplished by leaves, every hour of the day, is one which chemistry can 

 neither understand nor imitate. 



If -we cannot succeed in seizing and imitating the conditions of a fact relatively 

 so simple and so well defined, what must be our embarrassment when we would 

 analyze the chemical and physiological phenomena which result from it ? We see 

 in fact three simple bodies, rarely four, combining in indefinitely variable ratios> 

 and giving rise to the moat numerous and most different compounds; wood, 

 starch, sugars, oils, wax, balsams, essential oils of agreeable odors, and infectious 

 matters, delicious fruits, and violent poisons, acids such as vinegar, and alkalies 

 as quinine or strychnine, substances coloring and colorless, and, in general, sub- 

 stances of which the infinite variety surpasses all that the imagination can con- 

 ceive of. It is not without dismay that we measure the depth of our ignorance "in 

 'the presence of such multiplied phenomena, the mechanism of which altogether 

 escapes our grasp. 



There are, however, certain ill-disciplined minds that would explain everything, 

 and above all, matters of which they are most ignorant. It has been said that 

 plants probably contain compounds of carbonic acid and nitrogen, forming during 

 the night and decomposing under the influence of light ; it has also been stated 

 that there exists in green leaves a sort of fermentation deriving its activity from 

 the sun and having for its special function the decomposition of carbonic acid. 

 These explanations have not only the defect of being illusory and conjectural, 

 they are also false, for, according to them, pounded leaves preserving the same 

 composition ought to continue the same functions, which is not the case. There 

 is also a whole school of naturalists- who content themselves with attributing the 

 vegetable functions to what they call life, a kind of inaccessible force which 

 should suffice to explain everything by the sole virtue of its name : these appear 

 to me to renounce every description of scientific progress, like the ignorant bigots 

 who explain all phenomena by saying that it is God who makes them. Without 

 doubt God regulates the world, but He allows us sometimes, to contemplate the 

 machinery. Undoubtedly, also, it is life that regulates the functions of beings ; 

 but before proposing it as the final cause and ultimate explanation of facts we 

 must know a little more what it is and what are the means it employs. It is 

 easily" seen to what feebleness we are reduced as soon as the ground of experiment 

 fails us, when to fill up the vacuum in our knowledge we take refuge in hypo- 

 theses, in unexplained and unexplanatory forces. Let us be true : we are ignor- 

 ant •, let us confess it, and gird up our loins and search ! 



To console ourselves for this avowal, which might be painful to our self love, to 

 encourage us in our labors of the morrow, let us, in dwelling upon their results, 

 measure the importance of the discoveries actually made. If plants give forth 

 oxygen, animals absorb it, and compensation is thus established between these 

 inverse functions. This might be experimentally demonstrated by enclosing 

 under a bell glass an animal and a plant. Separately , each of them would die 

 the first by drowning itself in the carbonic acid it would exhale, the second, 

 because deprived of this gas which nourishes it. Brought together in darkness, 

 the animal and the vegetable would injure instead of assisting one another ; but, 

 under the influence of the sun, the life of the one would support that of the other ; 



