154 PKACTICAL BOTANY 



cases, is only a temporary covering of the younger portion 

 of the root. The soil will be found in this case also 

 adherent to the fibrils, thus indicating the presence of 

 root-hairs at some distance from the apex, but not at 

 the extreme apex, nor on the older portion of the root 

 where the cortex has been thrown off. 



V. Select a strong young fibril : embed a short piece 

 of it, taken about half-way between the apex and 

 the beginning of the red colouring : cut transverse 

 sections, and clear with potash, or " eau de javelle " : 

 mount in glycerine, and examine under a high power : 

 observe 



1. The piliferous layer, a rather irregular layer 

 with slightly thickened outer wall : single cells may 

 have developed as root-hairs. 



2. The exodermis showing a thickening of the 

 radial walls not unlike that common in endodermis : this 

 thickening is continued all round the anticlinal walls, 

 and is not uncommon in roots of woody plants. 



3. Abroad band of ordinary cortex, with large inter- 

 cellular spaces : the walls are more thickened nearer 

 the central cylinder, and are pitted. 



4. The endodermis or bundle- sheath, with the 

 characteristic dot on the radial walls : within this is 

 the central cylinder, composed of 



5. A peripheral layer of the pericycle : occasional 

 periclinal divisions may be seen in the cells of this 

 layer. 



6. The groups of primary xylem usually four in 

 number which will be still separate from one another, 

 or, according to the age of the root, may be united at the 

 centre : note the details of appearance of this primary 



