8 



PRACTICAL BOTANY 



such sections when examined from a direction indi- 

 cated by the arrows (y y) will show the tangential walls 

 in surface view, while the radial walls, previously seen 

 in surface view would present their cut edges to the 

 observer. 



In the case of tangential sections only the central 

 part of the section (i.e. the part near to y y) is to be 



examined, for obviously in the more lateral parts of 

 the section (c D) the radial lines are cut not vertically 

 but obliquely. 



In all cases the sections must be cut accurately in 

 the plane intended : if the sections be cut obliquely 

 the difficulty of understanding the structure will in 

 almost every case be enormously increased. 



A razor of good quality is the best cutting instru- 

 ment : there is some variety of opinion as to the best 

 form of blade ; some prefer a hollow-ground razor, which, 

 though well suited for cutting small sections, will not 



