8 FOOD OF THE VEGETATING PLANT. CHAP. II. 



conclusion that has been drawn from it ; for Sene- 

 bier found that plants whose roots were immersed in 

 water took up less of the fluid in proportion as it 

 was mixed with water from a dunghill.* Perhaps 

 then the charcoal of water from a dunghill is held 

 merely in suspension, and enters the plant under 

 some other modification. 



But if carbon is not soluble in water in the state 

 of charcoal, in what other state is it soluble ? It is 

 soluble in the state of carbonic acid gas. But is 

 this the state in which it actually enters the root ? 



Opinion of On this subject phytologists have been somewhat 

 Sencbier. ,..,,. J . . ^ * 



divided m opinion. Senebier endeavours to prove 



that carbonic acid gas, dissolved in water, supplies the 

 roots of plants with almost all their carbon, and 

 founds his arguments upon the following facts : 

 In the first place it is known that carbonic acid gas 

 is soluble in water ; in the second place it is known 

 to be contained in the soil, and generated by the 

 fermentation of the materials composing manures ;-f~ 

 and in the next place it is known to be beneficial 

 to vegetation when applied artificially to the roots, 

 at least in a certain degree. This is evident from 

 the following experiment of Ruckert, as well as from 

 several experiments of Saussure's, previously related. 

 Ruckert planted two beans in pots of equal dimen- 

 sions,filled with garden mould ; the one was moist- 

 ened with distilled water, and the other with water 

 impregnated with carbonic acid gas. But the latter 



* Phys. Veg. vol. hi. p. 154-. f Ibid. vol. iii. p. 55, 



