18 OF 1H S ASSIMILATION OF CARBON. 



But it is inconceivable, that the functions of the organs of a 

 plant can cease for any one moment during its life, as long as 

 those organs are not exposed to the action of a process which 

 may counteract the performance of their proper functions. The 

 roots and other parts of it, possessing the stime property, con- 

 stantly absorb water and carbonic acid. This power is inde- 

 pendent of solar light. During the night, carbonic acid is accu- 

 mulated in all parts of their structure ; and the decomposition of 

 the carbonic acid, the assimilation of the carbon, and the exha- 

 lation of oxygen, commence from the instant that the rays of the 

 sun strike them. As soon as a young plant breaks through the 

 surface of the ground, it begins to acquire color from the top 

 downwards ; arid the true formation of woody tissue commences 

 at the same time. 



The atmosphere is constantly in motion, both horizontally and 

 vertically. The same spot is alternately supplied with air pro- 

 ceeding from the poles or from the equator. A gentle breeze 

 moves in an hour over six German miles, and in less than eight 

 days over the distance between us and the tropics or the poles. 

 When the vegetable kingdom in the temperate and cold zones 

 ceases to decompose the carbonic acid generated by the processes 

 of respiration and combustion, the proper, constant, and inex- 

 haustible sources of oxygen gas are the tropics and warm cli- 

 mates, where a sky seldom clouded permits the glowing rays of 

 the sun to shine upon an immeasurably luxuriant vegetation. In 



lime in four days, carbonic acid is extracted from the air, and the lime is 

 consequently converted, on the surface, into a carbonate. It has heen ac- 

 curately determined that one square decimetre receives in this way a coat- 

 ing of carbonate of lime weighing 6*732 grammes. Upon the 105 square 

 metres already mentioned there must accordingly be formed 7630 grammes 

 of carbonate of lime, which contain 4331*6 grammes of carbonic acid. 

 The weight of one cubic decimetre of carbonic acid being calculated at 

 two grammes (more accurately r9797S), the above-mentioned surface must 

 absorb in four days 2 - 193 cubic metres of carbonic acid. 2500 square me- 

 tres (one Hessian acre) would absorb, under a similar treatment, 51 £ cubic 

 metres = 1818 cubic feet of carbonic acid in four days. In 200 days it 

 would absorb 2575 cubic metres — 904,401 cubic feet, which contain 

 11,353 lbs. of carbonic acid, of which 3304 lbs. are carbon, a quantity three 

 times as great a9 that which is assimilated by the leaves and roots gro '*?:n$; 

 upon the same space. 



