STRUCTURE 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. 45. 
Fie. 42. — Portion of a Sieve-Tube, showing one whole cell and parts of two others. 
Fie. 43.— Longitudinal Section through Sieve-Tube of the Gourd. Z, cell-wall; 
h, outer coating of protoplasmic cell-contents i ; v, sieve-plate. 
Fig. 44. — Transverse Section of a Sieve-Plate like that shown at v. 
Fie. 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.) 
