ON THE SEED. 243 



Caroline. But for what purpose do they require this 

 accumulation of carbon, since they must part with it in 

 order to germinate ? 



Mrs. B. Carbon is a great antiputrescent, and is 

 necessary to prevent the seed from rotting previous to 

 being sown. Some seeds are, through its influence, ca- 

 pable of being preserved several centuries ; while others, 

 which are but scantily supplied with it must be sown as 

 soon as ripe. And in seeds which have not acquired a 

 due supply of this preservative, the principle of life is ex- 

 tinguished before they separate from the parent-plant. 



Emily. With a view of ascertaining whether seeds 

 are capable of germinating, I have seen gardeners throw 

 them into water ; discard those which swam on the sur- 

 face as worthless, and sow only those which sunk. They 

 judged by the weight of the seed, I suppose, whether it 

 contained a sufficient quantity of carbon to have preserved 

 the vital principle. 



Mrs. B. Or, rather, they know by experience that 

 heavy seeds are the most likely to germinate. Immers- 

 ing seeds in water has also the advantage of preparing 

 them for germination, by supplying them with the moist- 

 ure of which they stand so much in need. 



Emily. And it is, I suppose, the oxygen of the atmos- 

 phere which performs the office of relieving them from the 

 excess of that element with which they are encumbered? 



Mrs. B. Yes ; it is therefore necessary that the soil 

 should lie loosely and lightly over the seed, in order that 

 the air should have access to it. The oxygen of the at- 

 mosphere then combines with the carbon of the seed, and 

 carries it off in the form of carbonic acid gas. Seeds will 

 germinate in contact with air which contains from one 

 eighth to one third of oxygen : if the proportion be less, 

 it will be insufficient to perform the function required ; 

 if more, the excitement will be too great, and the seed will 

 perish from exhaustion. 



Emily. The proportion of one fifth of oxygen, which the 

 atmosphere contains, is, then, just the desirable medium. 

 And heat, I conclude, is also essential to germination ? 



1327. How long have some seeds been preserved, and by what means'? 



128. What would be the consequence if seeds were destitute of carbon! 



529. What effects on seeds are produced by immersing them in water! 

 1330. Why should the soil in which seeds are sown lie loosely! 1331 

 What portion of oxygen in the air is needed to make seeds germinate! 



