$2 OF THE COTYLEDONS. 



may grow less luxuriantly, and be more abundant in 

 blossoms and fruit. Dr. Darwin accounts for this from 

 the damage which the cotyledons may receive from 

 keeping, by which their power of nourishing the infant 

 plant, at its first germination, is lessened, and it be- 

 comes stunted and dwarfish through its whole duration. 

 Dr. Thomson of Edinburgh, in his System of Chem- 

 istry, vol. 4, 374, has published a very satisfactory ex- 

 planation of one part of the functions of the cotyledons. 

 Several philosophers have discovered that very soon after 

 the seed begins to imbibe moisture, it gives out a quan- 

 tity of carbonic acid gas, even though no oxygen gas be 

 present. In this case the process stops here, and no 

 germination takes place. But if oxygen gas be present, 

 it is gradually absorbed in the same proportion. At the 

 same time the farina of the cotyledons becomes sweet, 

 being converted into sugar. " Hence it is evident," 

 says this intelligent writer, " that the farina is changed 

 into sugar, by diminishing its carbon, and of course by 

 augmenting the proportion of its hydrogen and oxygen.* 

 This is precisely the process of malting, during which it 

 is well known that there is a considerable heat evolved. 

 We may conclude from this, that during the germina- 

 tion of seeds in the earth, there is also an evolution of 

 a considerable portion of heat. This indeed might 

 have been expected, as it usually happens when oxygen 

 gas is absorbed. So far seems to be the work of che- 

 mistry alone ; at least we have no right to conclude that 



* This is also the opinion of M, d;? Saussure, Recherchei 

 Chimiquea gur la Vegetation, fi. 16. 



