ENDOSKELETON. PLANTS. 3 



A. 3. Sections of the stem of a Wax-palm (Copernicia cerifera), 

 with a drawing illustrating its structure. On the phloem 

 (usually outer) side of each vascular bundle is a bundle of 

 thick-walled prosenchymatous cells of dark colour forming 

 a sclerenchyma that gives strength and stiffness to the 

 stem. In the flower-stem each vascular bundle is com- 

 pletely surrounded by a sclerenchymatous sheath. 



Micheels, Mem. Cour. Acad. Belgique, t. liii. 1893, p. 1. 



Bot, Centralbl., vol. lix. p. 186. 



A. 4. Transverse section of the stem of Black Ebony (Diospyros 

 melanoxylon). The outer portion of the wood (alburnum) 

 is of a pale colour and is concerned in the conduction 

 of sap. The central older " heart-wood " (duramen) is of 

 a dark colour, and has ceased to conduct sap. It serves to 

 give extra stiffness and strength to the stem. 



A. 5. Section of stem, portion of leaf, and drawings illustrating 

 the structure o the sclerenchymatous spicular cells, and 

 their arrangement in the leaf of Wehvitschia mirabilis. In 



Fig. 2. 



c. s. 



Arrangement of Spicular Cells in Leaf of Welwitschia. 

 Vert long. sect, x 20. 



this plant, as in many others, certain cells of the funda- 

 mental tissue ( = tissue between epidermis and vascular 

 bundles) depart from the usual character of the funda- 



B'2 



