106 VEGETABLE HISTOLOGY. 



Sections may be mounted directly from this into balsam. 

 Aniline oil may be used in the same way. Aniline is kept free 

 from water by placing in it a stick of solid caustic potash. 



SCHULZE'S MACERATION MIXTURE. One gram of potassium 

 chlorate dissolved in 50 cc. of nitric acid, generally of specific 

 gravity 1.3, but the strength of the acid may be varied to suit 

 the specimen. It is used for the isolation of cells. Sections 

 are placed in the solution and gently heated until the reddish 

 color which first appears in the tissue has disappeared. The 

 whole is then poured into a large quantity of water to stop 

 action and washed well with water. The cells will now be 

 found easy to separate. Sections should not be carried from 

 alcohol to the mixture, but always from water, to avoid violent 

 action. Care is needed to stop the action at the right point. 

 The work should be done under a fume-hood. 



AMMONIO-COPPER HYDROXIDE (Schweitzer's reagent). This 

 should be freshly prepared when needed by dissolving some pre- 

 cipitated copper carbonate in concentrated ammonia water. 

 The copper carbonate is obtained by adding sodium carbonate 

 solution to a solution of copper sulphate and thoroughly wash- 

 ing and drying the precipitate by exposure to the air. Schweit- 

 zer's reagent is a good solvent for cellulose. 



PRESERVING FLUIDS. 



1. Alcohol. Pass objects from weaker to stronger solutions 

 50 per cent., 70 per cent., 90 per cent. 



2. Glycerin. Pass from weaker to stronger glycerin. 



3. One per cent, solution carbolic acid in water. 



4. Aqueous solution corrosive sublimate. 



5. Aqueous solution of formaldehyde, 2 to 3 per cent. 



B. SECTION CUTTING AND PROCEDURE IN MAKING A PERMANENT 



MOUNT. 



SECTION CUTTING. 



Only very thin objects are suited for examination under the 

 microscope, and the higher the power the thinner must be the 

 object. It is evident that in order to study large bodies, as the 

 organs of plants, thin slices or "sections" must be made. Such 

 sections should be of as nearly equal thickness in all parts as 

 possible. A transverse section is one at right angles to the 

 long axis of the object. A longitudinal section is one parallel 

 to the long axis of the object. In the case of cylindrical objects, 

 as a stem, there are two kinds 



1. Longitudinal radial section, which lies in the plane of the 

 radius. 



