vin.] THE BEAN-PLANT. Si 



working from the medullary cavity outwards, note 

 the following layers, using at first a low power : 



a. The pith-cells : much as in the transverse sec- 

 tion. 



b. The fibre-vascular bundles presenting- 



a. The spiral vessels: elongated tubes with a spiral 

 thickening on their walls. 



(3. The wood-cells: elongated and with much 

 thickened walls. 



y. The dotted ducts: much like , but the thick- 

 ening not deposited in the form of a spiral. 



8. The cambium zone: made up of cloudy- 

 looking, small, angular, thin-walled cells. 



e. The bast parenchyma : thin-walled elongated 



cells. 

 . The bast vessels: larger elongated cells with 



oblique perforated septa (sieve-tubes]. 



77. The bast fibres, fusiform and thick-walled. 



c. More parenchymatous cells. 



d. Epidermis: composed apparently of cubical 

 colourless cells : here and there the opening of 

 a stomate (d. 2. d. (3) may be seen. 



J )ra\v the section. 



5. Compare the transverse and longitudinal sections 

 together, making out the corresponding parts in each. 



6. Put on a high power, and examine each of the above- 

 mentioned tissues carefully. 



7. Stain with iodine : note the cell-walls ; the protoplasm 

 its presence or absence, and relative quantity in 

 the various tissues ; the nuclei of the cells ; starch 

 granules in some, stained deep blue by the iodine. 



M. 6 



