72 PRACTICAL BOTANY 



glycerine ; examine them with a high power for sieve-tubes. 

 The general arrangement of the phloem is similar to that in 

 the Elm. The sieves, which will appear stained pink, occur on 

 oblique walls facing the radial plane, and are therefore here 

 seen in surface view. Note that they have a similar appear- 

 ance to those above described, but here three or more sieve- 

 plates occur on each oblique wall. 



II. Cut tangential sections of the same ; stain, and mount as 

 before. The oblique walls are here cut longitudinally ; the 

 sieve-plates are often callous, especially in autumn. 



Note the form of the segments of sieve-tubes ; it is 

 fundamentally the same as that of the cambium cell as seen in 

 tangential section (compare Fig. 7, C, D). 



