HISTOLOGY OF ANGIOSPERM STEM, ROOT, ETC. 107 



and pour the contents of the tube on a filter, then wash 

 (with the wash-bottle of water) the macerated tissue on 

 the filter paper ; or pour the contents of the tube into a 

 large dish of water. 



Transfer the macerated tissue to a drop of glycerine on 

 a slide, and tease it out and cover the isolated tissue con- 

 stituents. In the xylem the most abundant elements are 

 the fibres in the case of Lime-tree ; note also the vessels, 

 tracheids, and parenchyma- cells (often still in vertical 

 rows). The most conspicuous phloem elements are the 

 fibres much longer than those of the xylem and with 

 thicker walls. 



Other woody stems (e.g. Oak, Elm) should be studied 

 by the maceration method, together with thin transverse 

 and longitudinal (radial and tangential) sections. 



122. The Development of Fhellogen (Cork-cam- 

 bium) is easily followed in the Elder (Figs. 31, 32). Cut 



Fig. 1. Transverse Section of Stem of Elder, showing three Lenticels. 



transverse sections of an Elder twig where the surface is 

 beginning to change from green to grey or brown, and 

 note that tangential divisions have appeared in the outer- 



