THE ACOEN AND ITS GERMINATION 17 



relatively very long and very narrow cells, the minute 

 structure of which we will riot 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, A). 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 



