PRACTICAL WORK. NO. IV. 207 



b. phloem, consisting of 



(1) sieve tubes or phloem vessels, mostly empty, 

 except where sieve plates occur; 



(2) much smaller companion cells filled with proto- 

 plasm ; 



(3) a variable amount of phloem parenchyma. 



c. cambium, consisting of small brick-shaped cells. 



d. xylem or wood towards the centre of the stem, 

 and consisting of larger vessels next the cambium and 

 occasionally packed in with wood fibres, and radiating rows 

 of smaller vessels of the protoxylem, packed in with wood 

 parenchyma. 



Your sketch should also show the beginning of the 

 interfascicular cambium, where a few cells in the medul- 

 lary rays next the cambium have begun to divide tan- 

 gen tially. 



[A permanent preparation may be made by mounting 

 in glycerine a section that has been washed in water, and 

 enclosing the coverslip with a ring of gold size, stiff 

 balsam, or brunswick black.] 



ii. Cut a small piece of stem in half longitudinally. 

 Hold a piece (about J inch long) in your fingers, and cut 

 longitudinal sections that shall pass through a vascular 

 bundle. Mount as before and show on your sketch 



a. pith consisting of rectangular thin-walled cells 

 (parenchyma) ; 



6. spiral vessels; 



c. dotted vessels ; 



d. cambium ; elongated cells containing protoplasm 

 and nucleus ; 



e. phloem vessels or sieve tubes ; 



