144 METHODS OF MICROSCOPICAL RESEARCH. 



5. "Wash thoroughly in water. 



6. Place in alcohol for ten minutes. 



7. Clear in xylol and phenol, mount in xylol 

 balsam. 



Picro Carmine, Double Staining. 



Picro Carmine as a selective double stain cannot 

 be surpassed. The process is as follows : Take of 

 carmine 2 grains, liquor ammonia ^ drachm, dis- 

 tilled water 1 ounce ; dissolve the carmine in the 

 ammonia by means of gentle heat, add the water. 

 Dissolve 8 grains of picric acid in 1 ounce of alcohol, 

 also by means of gentle heat, and mix the two 

 solutions. 



Place the sections in alcohol for one hour; im- 

 merse them in the recently filtered staining solution 

 for from half an hour to three hours, i.e., until they 

 are sufficiently stained ; wash them in alcohol, 

 immerse them in an alcoholic solution of picrate of 

 ammonia for one hour, and for a second hour in a 

 like solution ; in other words, change the solution 

 once during the two hours. Place them in alcohol 

 for a few minutes, clear in xylol and phenol as 

 already described, and mount in xylol balsam. 



Unstained vegetable specimens may be mounted 

 in balsam, glycerine jelly, or Farrant's medium. 



The Preparation of Diatomacese. 



Diatoms may be said to be absolutely ubiquitous ; 

 recent and fossil, living or dead, they are readily 

 obtainable in vast numbers, and of infinite variety. 

 In nearly all waters, fresh or salt, still or running, 



