CH. Ill] 



ROOT. 



35 



ness or irritability. This quality of growth which enables 

 a root to grow straight down into the ground is of 

 obvious use to it, for it thus fixes itself most quickly and 

 most effectively in the soil in which it has to play its part 

 in the plant's economy. Before going on to the functions 

 of the root it will be well to consider its structure. 



FIG. 13. 



TRANSVERSE SECTION OF THE ROOT OF Vicia Faba (semi-diagrammatic). 

 p.l, piliferous layer bearing root hairs. 

 c, cortex, the cells of which are not shown. 

 end, endodermis. 

 p.c, pericycle "\ 



x, xylem I central cylinder, or stele ; see Preface on 

 phi, phloem | the use of this term. 

 p, pith J 



Fig. 13 represents a transverse section of the primary 

 root of a bean not far behind the tip, as seen with a 

 low power of the microscope. In the centre of the section 

 is a circular mass of cells differing in texture and aspect 



32 



