94 PLANT LIFE 



(Figs. 13A and B). A fairly young stem cut 

 across and examined under a moderate magni- 

 fication shows that the centre is occupied by 

 a bulky pith around which are seen the cut 

 ends of the conducting strands the vascular 

 bundles. Just outside these are to be found 

 the cut ends of small rod-like strands of tissue, 

 the sclerenchyma. These run down the stem, 

 following, roughly, the course of the vascular 

 bundles. They are connected laterally at 

 intervals, and especially at a node where a 

 leaf springs from the stem. Each of these 

 sclerenchymatous strands consists of very 

 much elongated cells with pointed ends that 

 grow and insert themselves between their 

 neighbours above and below, thus giving the 

 rod or strand of sclerenchyma as a whole a 

 considerable degree of tenacity. 



The walls of the cells become greatly 

 thickened, -.and the rod is sharply marked off 

 from the soft tissues of the rind in which it 

 is embedded. Regarded from the point of 

 view of its physical properties it exhibits 

 remarkable! strength. It is quite elastic even 

 when submitted to considerable stress. This 

 means that within certain limits it can be 

 pulled out (i. e. elongated) by applying a 

 force, and when this is withdrawn it will 

 recover, and contract to its former length. 

 In this respect the sclerenchymatous strands 

 of many plants are but little inferior to good 

 steel, and a strand one millimeter in cross 

 section will stand a pull of about twenty 



