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OF THE COTYLEDONS.

neither does it cause their premature germination,unless accompanied by some action of the air.

It is usual with gardeners to keep Melon and Cu-cumber seeds for a few years, in order that the fu-ture plants may grow less luxuriantly, and be moreabundant in blossoms and fruit. Dr. Darwin accountsfor this from the damage which the cotyledons mayreceive 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 throughits whole duration.

Dr. Thomson, of Edinburgh , in his System of Che-mistry, vol. 4. 374, has published a very satisfactoryexplanation of one part of the functions of the cotyle-dons. Several philosophers have discovered that verysoon after the seed begins to imbibe moisture, it givesout a quantity of carbonic acid gas, even though nooxygen gas be present. In this case the process stopshere, and no germination takes place. But if oxygengas be present, it is gradually absorbed in the sameproportion. 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 diminish-ing its carbon, and of course by augmenting the pro-portion of its hydrogen and oxygen*. This is pre-cisely the process of malting, during which it is well

* This is also the opinion of M. tie Saussurc, Rccherches C/dmiqucssur la Vegetation, p. 16.