The Preparation of Whole Mounts and Sniears 103 



Dissolve the gelatin in the water at 35°C.; then add the other 

 ingredients. Filter while warm through fine silk or coarse filter paper. 

 This mounting medium keeps well. Materials to be mounted in 

 glycerin jelly are first stained (if necessary) , then dehydrated by the 

 glycerin evaporation process. For filamentous algae and fungi the 

 most satisfactory stains are the self-mordanting hematoxylins and iron 

 hematoxylin. Staining trials can be made with small quantities of 

 the plant material until a satisfactory schedule is worked out. Then 

 stain a large batch, and dehydrate by the glycerin method. To make 

 a slide from the dehydrated material, place a piece of glycerin jelly 

 about as large as a match head on a clean, dry slide, and warm until 

 melted. Remove a quantity of the plant material from the pure 

 glycerin, draw off excess glycerin with filter paper, and put the plant 

 material into the warmed jelly. Lower a cover glass carefully over 

 the material. If the material is not excessively fragile, a lead weight 

 on the cover glass will squeeze out excess jelly and make a thinner 

 mount. AVhen the jelly is cool, clean off any excess around the cover 

 glass and seal around the edge of the cover glass with a quick-drying 

 lacquer such as Duco. Sealed preparations will keep for several years, 

 but it is well to remember that the mounting medium is soft. Such 

 preparations are not desirable for use by elementary students. 



Permanent Slides of Whole Mounts 



Permanent stained slides in a hard, durable mounting medium 

 are much more satisfactory than soft, easily damaged, temporary or 

 semipermanent slides. Modern methods make possible the rapid, 

 quantitv production of permanent slides almost as quickly and easily 

 as the making of old-fashioned semipermanent slides. Filamentous 

 algae and delicate objects may be killed in any of the formulas de- 

 scribed in the foregoing pages. Wash out the killing or storage fluid 

 with water and apply an appropriate stain. Any of the self-mordanting 

 hematoxylins will give excellent results. It is best to overstain strongly, 

 leaving the material in the stain for 1/2 to 1 hr. Wash in distilled 

 water until the rinse water is no longer tinted. Destain in 1/10' < HCl. 

 Cover the material with the acid in a shallow dish and agitate gently. 

 After 1 to 2 min. drain, rinse in tap water, and examine with a 

 microscope. Repeat the treatment in acid until only the nuclei and 

 pyrenoids remain blue-black, then wash thoroughly in tap water. 



Iron hematoxylin will give the most critical staining of nuclear 

 structures and pyrenoids. Mordant algae for 1 to 2 hr. Rinse quickly 

 but thoroughly in distilled water and stain for 2 to 8 hr. Destain by 



