442 THE UNIVERSE. 



Under the influence of light and temperature plants ex- 

 hibit various movements. So great is the action of these 

 upon the organism that it is entirely changed. This is what 

 we see happen in their sleep, which, as we have seen, pre- 

 vents certain species from being recognized, and totally 

 changes the look of a meadow or forest. 



It is particularly in the leaves that we meet this remark- 

 able phenomenon, which approximates plants so much to 

 animal life. 



198. Semaphore Plant: Desmodia oscillans. 



Tn this respect the Semaphore plant (Desmodia oscillans) 

 ought to occupy the first place ; the mobility observed in it 

 surpasses enormously that of many inferior animals. It is 

 an Indian plant of the family of Leguminosao, each leaf of 

 which is composed of a great terminal leaflet and two 

 smaller ones which approximate at its base. When the sun 

 falls upon the Desmodia, these two leaflets go through a 

 very remarkable series of continuous oscillations. They ad- 

 vance and retire successively one from the other with a 

 trembling, jerking movement, which resembles that of the 

 seconds-hand of a watch or the arms of a semaphore tele- 



