366 SCOTS PINE. 



ring of vascular bundles, separated from each other by 

 (3) the primary medullary rays, bands of parenchyma 

 continuous externally with (4) the parenchyma of the 

 cortex and internally with (5) that of the pith. In each 

 bundle note the internal xylem consisting of regular radial 

 rows of thick-walled lignified elements, and the external 

 phloem with cellulose walls, with the cambium between 

 them ; in the cortex, note the large resin-ducts, the 

 cavity of each duct lined by a layer of small epithelium 

 cells. 



518. T. S. of Current Year Stem. In transverse 

 sections of the current-year stem note 



(1) The wavy outline of the section, owing to the bases 

 of the scale-leaves. 



(2) The epidermis, a layer of cells with the outer walls 

 thickened and covered by a distinct cuticle. 



(3) The cortex, consisting of more or less rounded cells 

 with cellulose walls, some containing starch, others tannin, 

 while the outer cells have chloroplasts. 



(4) The resin-ducts in the cortex. 



(5) The cork and cork-cambium, lying immediately 

 below the epidermis, in regular radial rows. 



(6) The complete ring of vascular tissue phloem and 

 xylem separated by cambium, the originally separate 

 bundles having become joined up by the inter-fascicular 

 cambium. 



(7) The wavy inner outline of the xylem, the portions 

 projecting into the pith showing the position of the primary 

 bundles and containing the protoxylem. 



(8) The pith, consisting of parenchyma like that of the 

 cortex but without resin-ducts. 



(9) The medullary rays, some extending right from 

 cortex to pith through the whole vascular cylinder 

 (primary rays), others passing only part of the distance 

 inwards and outwards from the cambium (secondary 

 rays). 



( 10) The resin-ducts in the secondary xylem. 



Keep the sections for comparison with those of the older 

 stem. 



