244 TEANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



deposit been formed, through and through the tissues of 

 the root, only a slight deposit is formed on the stem and 

 leaves. This difference is due to the presence of a 

 resistant cuticle on the stem and leaves and the experi- 

 ment is an easy way of shewing that the surface of the 

 root is absorptive for watery solutions of salts, whilst the 

 surfaces of the stem and leaf are so modified as to resist the 

 infiltration of water. 



On examining the root microscopically by means of 

 transverse sections no actual granules of deposit are to be 

 seen internally or externally with either low or high 

 powers. The deposit is not on but in the external tissues. 

 The walls of the epidermal and outer cortical cells are 

 seen to be distinctly brown and the protoplasms and nuclei 

 of these cells have also assumed a brownish tint. This 

 colouration is due to a deposit of the oxide of man- 

 ganese in an almost molecular state of subdivision. On 

 treating the sections with warm dilute hydrochloric acid 

 the brown deposit is dissolved, the cells and cell walls 

 becoming quite uncoloured and the solution thus obtained 

 readily gives the borax bead test for manganese. If the 

 radicles are left in the permanganate solution for too long 

 a period of time they become browned throughout their 

 entire thickness and are at the same time killed. But if 

 the roots are removed from the solution as soon as it has 

 penetrated the epidermis and the layer or two of cortical 

 cells immediately beneath and are then placed in a fresh 

 well aerated nutrient saline solution, their growth tempor- 

 arily checked by the immersion in the permanganate 

 solution is soon resumed. The central unpermeated part 

 of the root alone grows and increases in length, the outer 

 dead part remaining of the same length. The conse- 

 quence is that the outer brown coat splits into rings over 

 the growing region or regions and between these rings 



