SOME COMMON OBJECTS 51 



its contents. You will note the cell wall, which 

 surrounds and encloses the contents, a film of proto- 

 plasm forming an inner lining to the cell wall, and 

 what may seem to be an emptj^ cavity in the centre 

 of the cell, which is reallj^ filled with sap, and is 

 called the " vacuole." Pale green chloroplasts with 

 chlorophyll grains, which are the green colouring 

 material of plants, will be seen among the cell 

 contents. 



Probably the contents enumerated will be all 

 that can be detected up to this point. To make 

 observation easier we proceed to stain the hairs with 

 iodine solution. This solution is prepared by taking 

 10 grains of iodine, 5 grains of potassium iodide, and 

 making a clear solution in distilled water, about 

 2 ounces. To stain the hairs, place drop after drop 

 of iodine solution on the slide at one edge of the 

 cover-glass, but do not allow any of it to flow on top 

 of the cover. Then hold a small piece of blotting 

 paper to the opposite edge of the cover. The 

 blotting paper will soak up the water in which the 

 hairs are mounted, and the iodine solution wiU be 

 drawn into its place . When the stain has thoroughly 

 permeated the hairs they are ready for further 

 microscopic examination. We are now able to 

 observe the cell and its contents with greater clear- 

 ness. The cell wall is barely, if at all, stained. The 

 stain will have so affected the protoplasm that it is 

 coloured yellow or nearly brown. The little chloro- 

 phyll bodies will have assumed a dingy purplish 

 colour. But the point of interest is the appearance 

 of a tiny oval body within the film of protoplasm. 

 This body is the nucleus, which will be more deeply 



