THE ACORN AND ITS GERMINATION. 17 



surfaces of extremely delicate strands or cords of rela- 

 tively 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 em- 

 bryo, 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 be- 

 neath its tip, and that these pass into the two coty- 

 ledons, and there branch and run in long strands to- 

 wards 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 limit- 

 ed by an epidermal tissue and transversed 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 pres- 

 ent. The polygonal cells of the fundamental tissue of 

 the cotyledons are crowded with numerous brilliant 

 starch grains, of an oval shape and pearly luster, and 

 these lie imbedded 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 



