3^2 On Vegetation. 



every case be relative to the nature of each plant, as to its 

 exhausting power. 



M. Baisse proved that plants growing in water tinged 

 with madder become red ; and Bonnet iound them black 

 on growing in ink. These prove that the roots of plants 

 can take up coloured water, and deposit the colouring mat- 

 ter in the inte.-ior of the growing vegetable. On the same 

 principle they take up waier holdmg carbon in solution, and, 

 depositing the same iii the interior of the plants, contribute 

 to their increase. 



If we compare then this manner of Increase of carbon in 

 a plant, witli the disengagement of oxygen in the light, 

 carbonic acid in the dark, and the temperature of plants 

 duriniT ve2,etation, we shall find that, during that process, 

 cold is produced when the plant is acted upon by the sun, 

 and warmth when under contrary circumstances. In the 

 former case, the decomposition and evaporation of the wa- 

 ter cause absorption of caloric, while one cause only tends 

 to its disengagement ; namely, the combination of the 

 carbon, hydrogen, and other constituent parts of the plant, 

 whence it is probable cold is produced. While in the latter 

 case, and in the absence of the sun, the formation of car- 

 bonic acid, by the carbon in the plant, and the oxygen of 

 the atmosphere, must produce heat, owing to the different 

 capacities of those gases for caloric : in other words, the 

 quantity of con)bined caloric being greater in the oxygen 

 gas than is required by carbon for maintaining its aeriform 

 acid state, the superabundant portion becomes free, and 

 sensible heat is produced. 



It follows, from the above recited experiments, that car- 

 bon, in a state of solution in water, is taken up by the 

 radical fibres of vegetables and deposited within the plant, 

 in the same manner as colouring particles are found to be, 

 thus constituting the real pabulum of the vegetable king- 

 dom, without the presence of which in the soil no seed can 

 of itself vegetate beyond that degree of perfection which its 

 own innate carbon may allow of, as the crisis stamped by 

 nature as that wherein it is in a condition to shift for itself, 

 provided the food proper to that intent is within its reach. 

 Exclusive of the mode of operation, and degrees of fertility 

 of different manures dependent on ihe greater or less state 

 of solubility of their contained carbon, another, not less 

 important act of vegetation, deduced from the abjve, is the 

 augmentation of the temperature of the atmosphere by 

 plants when not exposed to solar light, as also the dimi-r 



nution 



