146 SCOTCH PINE. 



b. The shapes of the cells in the xylem and the grad- 

 ual transition into the cortical parenchyma. 



c. The contents of the cells. 



14. The bases of the scale leaves. (As they are closely 

 attached to the stem, and the lower portions not dis- 

 tinguishable from it, their transverse section is most 

 conveniently studied at this time.) Note the two 

 layers : 



a. The inner ; cells very thin-walled and irregular, 

 apt to be distorted in cutting. 



b. The outer ; composed of one or two rows of large 

 cells, sclerenchyma (note shape), and a single outer- 

 most row of smaller cells, the epidermis. Note 



i. The thickening of the outermost wall of the 



epidermis. 



ii. The continuous layer covering this wall, the 

 cuticle. 



15. Draw a part of the section, filling in sufficient to show 

 the structure completely. 



Cut a longitudinal radial section of a year-old stem. 

 Examine with a low power, and make out 



1 6. The same areas as seen in transverse section, in this 

 section appearing as strips : 



a. The////? j its regular margins. 



b. The xylem. Note 



i. Patches* of transversely placed cells, the 



medullary rays. 

 ii. The resin ducts j showing as one or two lighter 



streaks in the xylem. 

 iii. The two growth rings. 



c. The cambium ; a very narrow whitish strip. 



d. 'The phloem ; compact and fibrous-looking. 



e. The cortical parenchyma. 



