106 THE ART OF CULTURE. 



direct solar rays, chloride of carbon is immediately produced ; 

 but the same compound can be obtained with equal facility in 

 the diffused ligh of day, a longer time only being required. 

 When this experiment is performed in the way first mentioned, 

 two products only are observed (muriatic acid and perchloride 

 of carbon) ; whilst by the latter method a class of intermediate 

 bodies are produced, in which the quantity of chlorine constantly 

 augments, until at last the whole oil is converted into the same 

 two products as in the first case. Here, also, not the slightest 

 trace of decomposition takes place in the dark. Nitric acid is 

 decomposed in common daylight into oxygen, and peroxide of 

 nitrogen ; and chloride of silver becomes black in the diffused 

 light of day, as well as in the direct solar rays ; — in short, all 

 actions of a similar kind proceed in the same way in diffused 

 light as well as in the solar light, the only difference consisting, 

 in the time in which they are effected. It cannot be otherwise 

 in plants, for the mode of their nutriment is the same in all, 

 with the exception of certain parasites which obtained their car- 

 bon, either not at all, or only partially, from the original source ; 

 and their component substances afford proof that their food has 

 suffered absolutely the same change, whether they grow in the 

 sunshine or in the shade.* 



All the carbonic acid, therefore, which we supply to a plant 

 will undergo a transformation, provided its quantity be not 

 greater than can be decomposed by the leaves. We know that 

 an excess of carbonic acid kills plants, but we know also that 

 nitrogen to a certain degree is not essential for the decomposition 

 of carbonic acid. All the experiments hitherto instituted prove, 

 that fresh leaves placed in water impregnated with carbonic 

 acid, and exposed to the influence of solar light, emit oxygen 



* The impossibility of bringing to blossom and seed mosses and other 

 cryptogamous plants, in ordinary daylight, induced Mr. Noller, an excel- 

 lent botanist and chemist in Darmstadt, to form the opinion that the green 

 light from the leaves formed a necessary condition of their life. He 

 planted numerous kinds of these plants in mouldered wood placed in little 

 glass tubes, and covered the whole with a green glass globe. The experi- 

 ment established his view in a beautiful manner. All these elegant plants 

 developed under these conditions with the greatest luxuriance, and put 

 forth both blossoms and seeds 



