THE DIFFEBENTIATION OF THE PLANT-BODY 29 



cells of curious shape which extend from one epidermis 

 to the other. Others show bands of sclerenchyma sup- 

 plementing the veins and not infrequently enclosing them 

 and reaching the epidermis on each side. 



The supporting tissue is frequently known as the 

 stereome of the plant. It forms, as we have seen, the most 

 prominent part of the endo-skeleton. 



FIG. 32. DIAGRAM SHOWING THE CHIEF DISPOSITIONS OF THE SKELETAL 

 APPAKATUS IN A STEM WITH FIVE COLLATER/ L BUNDLES (IN TRANSVERSE 

 SECTION). 



(The sclerenchyma is black ; the bast of the bundles is white ; 

 the wood is dotted.) 



1, Type without accessory sclerenchyma ; 2, Equisetum ; 3, JBambusa ; 

 4, Pennisetum ; 5, Scirpus ; 6, Erianthus ; 7, Fimbristylis ; 9, Typha ; 

 10, Juncus ; 14, Cladium. (After Van Tieghem.) 



The cells of which the masses of sclerenchyma are 

 composed have been ascertained to possess almost as much 

 power of withstanding longitudinal strain as the finest 

 steel, and they are much more ductile than either this 

 metal or wrought iron. Their arrangement in the different 

 ways described has a very distinct relationship to the 

 character of the strain they have to resist. In such 

 structures as hollow stems where there is but little 

 substance of tissue, but where they are required to resist 



