234 THE INFLUENCE OF LIGHT ON LIFE, 



more (that is, if continual day supplanted the alternating order of 

 day and night). 



As we look round about upon the gardens of the world, and 

 observe the green leaves of the trees, the herbage of the fields, the 

 beautifully coloured flowers, and the myriad varieties of form into 

 which the vegetable kingdom is divided, we see them as they have 

 grown and been developed under the influence of day and night- 

 The same also applies to the animal world. In a general way, we 

 may say that all animals and all plants spend half their lives in 

 light and half in darkness, and that their present condition has 

 been arrived at under the influence of an equal amount of light 

 and darkness. Now, as each plant requires a certain quantity of 

 light for its successful growth, it is pretty evident that if that quan- 

 tity be unduly increased or unduly decreased, the consequences 

 thereof may be of a serious nature to the plant. By considering 

 what takes place, either in exceptional cases in the world of nature 

 or by actual experiment, when the norinal quantity of Hght is 

 greatly interfered with, we shall, perhaps better than in any other 

 way, understand the influence of light, and learn how important it 

 is that in our daily life we should not forget the beneficial results 

 which follow from a right relation between the rays of the sun and 

 the living things upon this planet, or ignore the consequences 

 which may follow if that relation be not attended to. The force 

 or reason of these statements may perhaps become more manifest 

 as we proceed. 



The carbon which a plant requires in order to build up its cells 

 and tissues is obtained from the carbonic acid gas which is con- 

 tained in the air. Carbonic acid gas, as we all know, consists of 

 carbon and oxygen; but as it is only the carbon which the plant 

 requires, it is therefore necessary that the compound should be 

 broken up, so that the requisite carbon may be obtained. Now, 

 living plants possess this wonderful power, and are able to extract 

 the carbon and set free the oxygen, but they are only able to exert 

 this power under the influence of light. During the day, therefore, 

 this process goes on without interruption ; but during the night the 

 plant is no longer able to continue it, as the influencing power, the 

 light, is of course absent. No sooner, however, does the morning 

 light once more bathe the plant than once again it is enabled to 

 appropriate the carbon. 



