

THE MICROSCOPE. 31 



for examining it. The petals of plants, the wings and 

 other parts of insects, with many other objects, can 

 only be examined in this way. 



Fig. 15. Stage Forceps. 



Even the beginner will find it useful to keep by 

 him some little bottles, containing certain chemical 

 re-agents. Thus, a solution of iodine is useful to 

 apply to the tissues of plants, for the purpose of 

 ascertaining the presence of starch. This solution 

 may be made by adding five grains of iodine and five 

 grains of iodide of potassium to an ounce of distilled 

 water. It turns starch blue and cellulose brown 

 Cellulose is the substance that forms the walls of 

 the cells in plants. Dilute sulphuric acid (1 to 3) 

 is also useful as a re-agent ; if applied to cellulose 

 previously stained with iodine, it imparts a blue or 

 violet tint. Strong nitric acid turns albuminous 

 matter a deep yellow; and when diluted (1 to 4) 

 with water is used for separating the elementary 

 tissues of vegetable substances either by boiling or 

 maceration. 



The strong solution of potash (liquor potassae) 

 can also be employed with advantage in softening 

 and making clear opaque animal and vegetable 

 substances. While using these powerful agents, 

 great care should be taken to prevent the trans- 

 parency of the object-glass becoming impaired by 

 contact with them or by long exposure to their 

 Vapours. 



