STETTCTUEB OF THE STEM. 



55 



Make 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. 44. 



Pig. 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 ; v, sieve-plate. 



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



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

 plates p on the sides of the tube (two of which are also shown on Fig. 43). 

 (All greatly magnified.) 



