174 The Influence of the Soil 



prove that they do possess this power. He placed a hya- 

 cinth-bulb in a vase filled with distilled Avater, and hermeti- 

 cally sealed. The leaves grew to the length of 6 or 7 inches, 

 and the total weight of carbon in the plant increased to 47,166 

 grains. Another bulb, placed in pounded quartz, presented 

 the same phenomena. Now, these two plants vegetated in a 

 space containing 50 cubic inches of air, and consequently on- 

 ly 0,08 grains of carbon ; it could not then be from the atmo- 

 spheric air alone that the plants imbibed this principle. In 

 M. Braconnot's experiments, small plants of white mustard, 

 which had germinated in sand, increased in weight in the pro- 

 portion of 0,206 to 0,234, under the influence of light alone. 

 The experiments of Gceppert, ('Nonnulla de plantarum nu- 

 tritione'), give quite opposite results ; the quantity of carbon 

 did not increase: those of John lead to analogous conclusions. 

 These contradictory experiments nevertheless agree in prov- 

 ing the influence of external agencies. That of water, which 

 can by itself nourish plants, has been proved by the trials of 

 Duhamel, Hasenfratz, De Saussure, and Crell, who raised 

 plants in marble, pounded quartz, horse-hair, &c. by water- 

 ing them with spring or river water. The experiments of 

 Hales, Percival, Ruckert, and De Saussure, demonstrate that 

 the carbonic acid is decomposed under the influence of light. 

 The last physiologist has made it evident that this decompos- 

 ing power is very energetic, since seven plants of periwinkle, 

 occupying a space of half a cubic inch square, decomposed 

 21,75 cubic inches of carbonic acid gas in six days. The ex- 

 periments of Link also prove that it is not sufficient for the 

 plant to receive carbonic acid, by the intervention of water 

 penetrating through its roots, in order that all the stages of 

 its vegetation and fructification may be accomplished ; but it 

 is further necessary that it should decompose that of the at- 

 mospheric air : it even appears, according to the observations 

 of M. Ad. Brongniart, that this mode of nutrition preponderat- 

 ed over the other, in antediluvian plants, which appears to in- 

 dicate that the composition of the atmosphere was different 

 then to what it is in the present day. 



We might have concluded from the preceding remarks, that 

 the nature of the soil could have no influence on the nutrition 

 of plants, carbonic acid appearing to be their only aliment ; 

 but we also find in their tissues, metals, alkalies, and salts, 

 which prove the influence of the soil in which they grow. — 

 Wahlenberg, however, founding his opinion upon facts pub- 

 lished by Vanhelmont, Boyle, Duhamel, Kraft, Bonnet, &c. 

 maintained that they were produced by the action of water 

 upon the tissues of the plant. 



