THE BEAN-PLANT. 81 



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. 



/?. The wood-cells: elongated and with much 

 thickened walls. 



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

 ening not deposited in the form of a spiral. 



S. The cambium zone: made up of cloudy- 

 looking, small, angular, thin-walled cells. 



. The bast parenchyma : thin-walled elongated 

 cells. 



. The bast vessels: larger elongated cells with 

 oblique perforated septa (sieve-tubes). 



17. 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. ft) may be seen. 



Draw 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 



