REAGENTS 31 



for an hour or even permanently. After material fixed in the alcoholic 

 solution has been washed in 50 per cent alcohol for an hour or more, 

 add the iodine solution used in testing for starch or even add, drop by 

 drop, tincture of iodine, until the color fails to disappear. With uni- 

 cellular forms, filamentous forms, and thin things, like fern prothallia, 

 such washing is likely to be sufficient, but with more bulky material 

 which is to be sectioned, the crystals may appear in the paraffin rib- 

 bon. In such cases, the slide should be dipped for a minute in the 

 iodine solution just before staining. 



Camphor may be used instead of iodine to hasten the washing, but 

 it does not give any color reaction. 



Material should be imbedded as soon as possible, since it gets 

 brittle if allowed to remain in alcohol. 



Kinoplasmic structures do not stain well with gentian violet, but 

 safranin and the haematoxylins stain almost as well as after chromic- 

 acid mixtures, and the carmines give their most brilliant stains, as a 

 result of the formation of mercuric carminate. 



The following formulas are merely suggestive: 



a) Corrosive sublimate and acetic acid. — 



Corrosive sublimate 3 g. 



Glacial acetic acid 5 c.c. 



Alcohol (50 per cent) or water 100 c.c. 



h) Corrosive sublimate, acetic acid, and formalin. — 



Corrosive sublimate 4 g. 



Glacial acetic acid 5 c.c. 



Formalin 5 c.c. 



Alcohol (50 per cent) or water 100 c.c. 



This is our favorite formula. For material which is to be mounted 

 in glycerin, glycerin jelly, or Venetian turpentine, use the aqueous so- 

 lution; for material which is to be imbedded, use the alcoholic. Ciha 

 are caught and preserved; and even delicate organisms, Hke Volvox, 

 do not collapse. 



c) Corrosive sublimate, acetic acid, and picric acid. — 



Corrosive sublimate 5 g. 



Glacial acetic acid 5 c.c. 



Picric acid, saturated solution in 50 per cent 



alcohol 100 c.c. 



Miss Ethel Thomas recommends tliis formula for the female game- 

 tophyte of Pinus. 



