OF THE COTYLEDONS. 77 



/ 



cumber seeds for a few years, in order that the fu- 

 ture plants 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 nou- 

 rishing the infant plant, at its first germination, is less- 

 ened, and it becomes stunted and dwarfish through 

 its whole duration. 



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

 mistry, vol. 4. 374, has published a very satisfactory 

 explanation of one part of the functions of the cotyle- 

 dons. Several philosophers have discovered that very 

 soon after the seed begins to imbibe moisture, it gives 

 out a quantity 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 cotyle- 

 dons 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 con- 

 clude from this, that during the germination of seeds 

 in the earth there is also an evolution of a considerable 



* This is also the opinion of M. de Saussure, Recherche* Chimiqitex 

 sur la Vegetation, p. 16. 



