STKTJCTUEE OF THE STEM. 



55 



Mate a thin section of the stem of grapevine or elder a year or two 

 old and study the pith with a power of 50 or 100 diameters. Sketch it. 



Fig 42. 



«!:lSSi^ -M—i) 



mm 



ULU. 43. 



D^ 



Fig. 44. 



Fig. 42. — Portion of a Sieve-Tube, showing one whole cell and parts of two others. 



Fig. 43. —Longitudinal Section through Sieve-Tube of the Gourd. Z, cell-wall; 

 A, outer coating of protoplasmic cell-contents i ; ^^ sieve-plate. 



Fig. 44. — Transverse Section of a Sieve-Plate like that shown at v. 



Fig. 45. —Part of Longitudinal Section of a Sieve-Tuhe of Linden, showing sieve- 

 plates j) on the sides of the tube (two of which are also shown on Pig. 43). 

 (All greatly magnified.) 



