372 INFLUENCE OF ACTINISM. 



absolute darkness sometimes necessary for the success 

 of the germinating process. We have seen that the 

 first operation of nature is purely a chemical one, but 

 this manifestation of affinity is due to an exertion of 

 force, which is directly dependent upon solar power. The 

 seed is buried in the soil, when the genial showers of 

 spring, and the increasing temperature of the earth, 

 furnish the required conditions for this chemistry of 

 life, and the plant eventually springs into sunshine. 

 Thus we obtain evidence that even through some depth 

 of soil the solar power, whatever it may be, is efficient, 

 .and that under its excitement the first spring of life, 

 in the .germ, is effected. 



The cotyledons and the plumule being formed, the 

 plant undergoes a remarkable change. The seed, like 

 an animal, absorbed oxygen and exhaled carbonic acid ; 

 the first leaves secrete carbon from carbonic acid in- 

 spired, and send forth, as useless to the plant, an excess 

 of oxygen gas. 



This power of decomposing carbonic acid is a vital 

 function which belongs to the leaves and bark. It 

 has been stated, on the authority of Liebig, that during 

 the night the plant acts only as a mere bundle of fibres, 

 that it allows of the circulation of carbonic acid and 

 its evaporation, unchanged. In his eagerness to support 

 his chemical hypothesis of respiration, the able chemist 

 neglected to inquire if this was absolutely correct. The 

 healthy plant never ceases to decompose carbonic acid 

 during one moment of its existence ; but during the 

 night, when the excitement of light is removed, and the 

 plant reposes, its vital powers are at their minimum of 

 action, and a much less quantity is decomposed than 

 when a .stimuiLatnig sun, by the action of its rajps, is 

 compelling the exertion of every vital function. 



During this process, we liave another example of 

 natural organic chemistry . The four inorganic elements 

 of which the vegetable kingdom is composed oxygen, 



