ABSOKPTION OF SOLAR ENERGY BY PLANTS. 75 



oxygen from hydrogen and carbon, and what becomes of it. 

 This force is no other than the light and heat force emanating 

 from the sun, rendered latent in the oxygen on the one hand, and 

 the carbo -hydrogen of vegetable tissue or secretion on the other, 

 and reproducible by the act of their recombination or combus- 

 tion. The sun's rays, for instance, falling upon the leaves of 

 the sugar-beet or sugar-cane effect an eventual decomposition of 

 carbonic acid into oxygen and sugar, thus : 



Garb-anhydride Water Sugar Oxygen " 



But the heat and light of the sun absorbed in this pulling apart 

 of oxygen and carbon, the one discharged into the atmosphere, 

 the other retained in the vegetable juices, are not lost, but ren- 

 dered latent in the oxygen and sugar respectively. Here I have 

 a mixture of sugar with a compound in which the oxygen of the 

 air has been accumulated, namely, chlorate of potassium, and on 

 touching the mixture with a drop of sulphuric acid on pulling 

 the trigger of the cross-bow, so to speak there is produced a 

 violent deflagration, in which the light and heat of the sun, 

 stored up in the separated sugar and oxygerT, are again manifested 

 to you by the combination of the two bodies with one another to 

 reproduce carbonic acid. The light and heat of this combus- 

 tion, and, indeed, of every combustion, are nothing more than the 

 light and heat of the sun, originally absorbed by the living plant, 

 and rendered latent in the tissue of the plant, and oxygen 

 of the air respectively. Even the heat evolved by the direct or 

 indirect combustion of zinc is no exception ; it is only the heat 

 stored up in the metal at the moment of its deoxidation by 

 means of the coal or charcoal in which the sun's force was in- 

 termediately retained. 



(80.) We see, then, in this way, that the vegetable organism is 

 a machine in which the sun's energy is absorbed in the pulling 

 apart of carbon and hydrogen from oxygen. The light and heat 

 force emanating from the sun is rendered latent in the separated 

 oxygen and carbo-hydrogen, just as human muscular force is 



