18 THE OAK 



pigment, composed of substances of the nature of 

 tannin ; 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 nutritious 

 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 quanti- 

 ties 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- 

 spicuous change ; and in any case it requires a period 

 of rest before the presence of the oxygen of the air and 

 the moisture of the soil are effective in making it ger- 



