THE ACORN AND ITS GERMINATION 17 
relatively very long and very narrow cells, the minute 
structure of which we will not now stay to investigate, but 
simply mention that these extremely fine cords, running 
in the main longitudinally through the embryo, are 
termed ‘vascular bundles’ (fig. 2,4). It may be shown 
that there is one set of them running up the central part 
of the radicle, starting from just beneath its tip, and that 
these pass into the two cotyledons, and there branch and 
run in long strands towards the ends of the latter. 
The three sets of structures which have been referred 
to are called ‘ tissues,’ and although they are still in a very 
young and undeveloped condition we may say that the 
embryo consists essentially of a large amount of thin- 
walled cell-tissue, of different ages, which is limited by 
an epidermal tissue and traversed by vascular tissue. 
At the tips of the radicle and plumule the cell-tissue 
is in a peculiar and young condition, and is known as 
embryonic tissue. 
As regards the contents and functions of these 
tissues, the following remarks may suffice for the pre- 
sent. The polygonal cells of the fundamental tissue of 
the cotyledons are crowded with numerous brilliant 
starch grains, of an oval shape and pearly lustre, and 
these lie embedded in a sort of matrix consisting chiefly 
of proteids and tannin, together with small quantities 
of fatty substances. 
In each cell there is a small quantity of protoplasm 
and a nucleus, but this latter is only to be detected with 
difficulty. Certain of the cells contain a dark-brown 
C 
