8 VITAL ACTIONS. 



bursts through its integuments; it then lengthens, 

 first in a direction downwards, next in an upward 

 direction, thus forming a centre or axis round which 

 other parts are ultimately formed. No known power 

 can overcome this tendency, on the part of the em- 

 bryo, to elevate one portion in the air, and to bury the 

 other in the earth ; but it is an inherent property with 

 which nature has endowed seeds, in order to ensure 

 the young parts, when first called into life, each find- 

 ing itself in the situation most suitable to its exist- 

 ence ; that is to say, the root in the earth, the stem 

 in the air. 



14. The conditions required to produce germina- 

 tion are, exposure to moisture, and a certain quantity 

 of heat ; in addition, it is necessary that a communica- 

 tion with the atmosphere should be provided, if ger- 

 mination is to be maintained in a healthy state. A 

 seed, when fully ripe, contains a larger proportion of 

 carbon than any other part, and so long as it is thus 

 charged with carbon, it is unable to grow. The only 

 means it possesses of ridding itself of this principle, 

 essential to its preservation, but forming an impedi- 

 ment to its development as a new plant, is by con- 

 verting the carbon into carbonic acid; for which 

 purpose a supply of oxygen is necessary. It cannot 

 obtain oxygen in sufficient quantity from the air, for 

 it is cut off from free communication with the air by 

 various means, either natural, as being enclosed in a 

 thick layer of pulp, or in a hard shell or stone ; or ar- 

 tificial, as being buried to a considerable depth below 

 the surface of the soil. It is from the water absorbed 



