[3] 71 ALG5J 



Spirogyra. 



A . Make a diagrammatic sketch of part of a filament under a low power, shewing the single row of similar 

 cells, containing the green spiral chloroplasts. 



B. Treat a fresh specimen with 5 % salt solution (by drawing a drop under the coverslip with blotting- 

 paper) and observe the shrinking of the protoplasmic lining. This phenomenon is known as plasmolysis. Sketch 

 a contracted cell. Draw water through with blotting-paper and observe the cell reassume its turgid condition. 



C. Mount the two preserved filaments of Spirogyra provided and stain with iodine. One has been fixed 

 after illumination and contains much starch, the other, kept for two days in the dark, contains no starch. 



D. Sketch a single cell under a high power shewing 



(a) the cell-wall ; 



(b) the spirally wound chloroplast with the pyrenoids, each of which is surrounded by starch-grains. Run 

 in iodine (by drawing a drop under the coverslip with blotting-paper) and notice that the starch surrounding the 

 pyrenoids is stained dark blue ; 



(c) the thin layer of colourless protoplasm closely pressed against the cell-wall ; 



(d) the nucleus suspended by strands of protoplasm ; 



(e) the large vacuole containing cell-sap. 



[Staining with iodine or with eosin may be necessary for d.] 



A. 



e 



