38 SOWING SEEDS. [CHAP. in. 



bon ; and when seeds germinate, they want to 

 absorb oxygen and to disperse their carbon. 

 Thus seeds and very young seedlings do not 

 require much light; it is, indeed, injurious to 

 them, as it undoes in some degree what warmth, 

 moisture, and air have been doing for them ; 

 but young plants, when they have expanded 

 two or three pairs of leaves, and when the 

 stock of carbon contained in their cotyledons 

 or in their seeds is exhausted, require light to 

 enable them to elaborate their sap, without 

 which the process of vegetation could not go 

 on. Abundance of light, also, is favourable to 

 the developement of flowers and the ripening of 

 seed*, as it aids the concentration of carbon, 

 which they require to make them fertile. The 

 curious fact, that seeds, though abundantly 

 supplied with warmth and moisture, will not 

 vegetate without the assistance of the air, was 

 lately verified in Italy ; where the Po, having 

 overflowed its banks near Mantua, deposited a 

 great quantity of mud on some meadows ; and 

 from this mud sprang up a plentiful crop of 

 black poplars, no doubt from seeds that had 

 fallen into the river from a row of trees of that 

 kind which had formerly grown on its banks, 

 but which had been cut down upwards of 

 seventy years before. Another instance oc- 

 curred in the case of some raspberry seeds 

 found in the body of an ancient Briton dis- 

 covered in a tumulus in Dorsetshire. Some of 

 these seeds were sown in the London Horti- 

 cultural Society's Garden at Turnham Green, 

 where they vegetated, and the plants produced 

 from them are still (1850) growing. Steeping 



