18 THE OAK. 



and a nucleus, but this latter is only to be detected with 

 difficulty. Certain of the cells contain a dark-brown 

 pigment, composed of substances of the nature of tan- 

 nin ; and small quantities of a peculiar kind of sugar, 

 called quercite, are also found in the cells, together with 

 a bitter substance. 



In the main, the above are stored up in the thin- 

 walled parenchyma cells as reserve materials, intended 

 to supply the growing embryo or seedling with nutri- 

 tious food ; the starch grains are just so many packets 

 of a food substance containing carbon, hydrogen, and 

 oxygen in certain proportions -, the proteids are similarly 

 a supply of nitrogenous food, and minute but necessary 

 quantities of certain mineral salts are mixed with these. 

 The vascular bundles are practically pipes or conduits 

 which will convey these materials from the cotyledons 

 to the radicle and plumule as soon as germination 

 begins, and I shall, say no more of them here, beyond 

 noting that each strand consists chiefly of a few very 

 minute vessels and sieve-tubes. The young epidermis 

 takes no part either in storing or in conducting the 

 food substances ; it is simply a covering tissue, and will 

 go on extending as the seedling develops a larger and 

 larger surface. 



We are now in a position to inquire into what takes 

 place when the acorn is put into the soil and allowed to 

 germinate. In nature it usually lies buried among the 

 decaying leaves on the ground during the winter, and it 

 may even remain for nearly a year without any con- 



