482 THE UNIVERSE. 



chemical phenomena. For its accomplishment it imperi- 

 ously demands a certain amount of warmth, water, and air. 

 If one of these factors be wanting, this first manifestation 

 of life becomes an impossibility. At the temperature of 

 zero all vegetation ceases. 



When cold fastens upon seeds it preserves them for an 

 indefinite period of time, just as it preserved the com- 

 panions of Bilbao, the discoverer of the South Sea, whose 

 corpses were recently found in the snows of the Cordilleras ; 

 and as it preserved the remains of the antediluvian ele- 

 phants and rhinoceroses, the skeletons of which, still envel- 

 oped in their flesh, were discovered in the ices of Siberia. 



The course taken by the water, which is to soak into the 

 grain and prepare the way for its evolution, is not always 

 the same. 



In seeds which have a coriaceous husk, not easily per- 

 meable by moisture, the liquid enters by the umbilicus. 

 Poncelet and De Candolle proved that all the outer surface 

 of these seeds might be covered with wax, and yet that 

 would not prevent them from germinating if the precaution 

 were taken of not covering the umbilical cicatrix. 



In seeds the skin of which is soft and easily imbibes 

 water, such as those of the haricot bean, for instance, it is 

 this structure that principally gives access to the water 

 which is so indispensably necessary to primordial life. 



The air also plays a great part in the chemical phenom- 

 ena of germination. The learned Homberg denied the im- 

 portance of it, because he saw seeds develop in the re- 

 ceiver of his pneumatic machine. But Boyle, Muschen- 

 broeck, and Boerhaave demonstrated that this agent is ab- 



