148 PRACTICAL BOTANY. 



chyma, which requires no further notice here. Outside 

 this is cork (and sclerenchyma at certain points), and at 

 the periphery of the section ~ 



6. The Epidermis. 



V. Cut tangential sections of a three or four years' old 

 branch, and bear in mind that as a rule the central part 

 of the sections is the most accurately tangential, i.e. 

 that the plane of section is there most accurately per- 

 pendicular to the radius of the stem. Mount as before. 



A, In sections which pass through the peripheral part 

 of the xylem observe 



i. The Tracheides of prosenchymatous form. No 

 bordered pits (or very few) are seen in surface view, but 

 they may be seen in large numbers in the radial walls 

 (here cut longitudinally) presenting a similar appearance 

 to that seen in transverse sections. 



ii. Medullary rays, which resemble a section of 

 a biconvex lens. Note that each ray extends only a 

 short distance in a longitudinal direction : in some 

 cases rays consist of only a single radial series of cells, 

 of which only one lenticular cell appears in this sec- 

 tion. Occasionally a resin-passage is included in a 

 ray. 



iii. Longitudinal resin-passages (cf. radial sections). 



B. In sections passing through the cambium will be 

 seen 



i. The Cambium-cells, resembling the tracheides in 

 form (prosenchymatous) ; cell-walls thin ; protoplasm 

 granular, with elongated nucleus. 



ii. Cambium of medullary rays, similar in 

 shape to the cells of the rays : thin-walled, with 

 granular protoplasm and nucleus. 



