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- 
