78 CHYMISTRY APPLIED TO AGRICULTURE. 



with the atmospheric air, or with water containing mucii 

 air. 



If seeds are secluded from air and moisture whilst fresh 

 and succulent, they putrefy ; but if previously dried, they 

 do not undergo this change, but preserve their power of 

 germination, till exposure to air and moisture calls it into 

 action. 



The activity of germination is proportioned to the de- 

 gree of oxygen contained in the air. The larger seeds 

 imbibe more of this gas than the smaller. 



Seeds, whilst germinating, exhale only carbonic acid ; 

 and the volume of oxygen they consume is always equal 

 to the volume of carbonic acid produced. All these 

 results have been ascertained by the beautiful experi- 

 ments of M. de Saussure. It appears, then, that the only 

 agent in germination is oxygen ; the only product car- 

 bonic acid. The seed parts with a certain portion of 

 carbon, and the oxygen combines with no other principle 

 of the seed. For if a seed be made to germinate in 100 

 inches of atmospheric air, containing 21 inches of oxygen, 

 it will be found that germination has produced 14 cubic 

 inches of carbonic acid, and that there remains 7 cubic 

 inches of free oxygen in the portion of atmosphere in 

 which the process of germination has been going on. 

 It is evident, then, that, in this first stage of vegetation, 

 water does not furnish the seed with any additional prin- 

 ciple, and that it is not itself decomposed. It is not, 

 however, useless to vegetation, since it is a well-known 

 fact, that well-dried seeds may be preserved from germi- 

 nation though brought in free contact with the air. 



Water appears to me to produce two undeniable effects 

 in germination. In the first place it penetrates the cover- 

 ing of the seed to deposit within it the oxygen of the air 

 which it holds in solution, in order to produce the forma- 

 tion of the first portion of carbonic acid ; and in the 

 second, it opens a free access by which the air can enter 

 into the grain, and act upon it in the manner already 

 pointed out. 



From what I have already stated, it follows, that ger- 

 mination cannot well be carried on, unless the atmo- 

 spheric air has access to the seed, which cannot be the 

 case if the seed be buried too deeply in the ground, or if 

 it be sown in a compact soil and closely covered over. 



It likewise follows, from these principles, that when the 



