STAINING THE NUCLEI OF YEAST CELLS 99 



4. Steady one edge of the cover-glass with the forceps 

 and pass the point of the dissecting needle just under the 

 opposite edge and raise carefully; the colony will be adher- 

 ent to it. 



When nearly vertical, grasp the cover-glass with the 

 forceps and remove it from the plate. Re-cover the 

 plate. 



5. Place the cover-glass specimen side up on desk and 

 cover with half a Petri dish until dry. 



6. Fix in the flame. 



7. Stain and mount as with ordinary cover-glass speci- 

 men, being careful to perform all washing operations with 

 extreme gentleness. 



EXERCISE 35. METHOD OF STAINING THE NUCLEI 

 OF YEAST CELLS 



The nuclei of yeast cells are not visible in unstained or 

 in ordinary stained specimens. A special method of pro- 

 cedure must be used. 



Apparatus. Clean cover-glasses; clean slides; forceps; 

 ferric ammonium sulphate, 3% aqueous solution; Ehrlich's 

 hematoxylin solution; two staining dishes for slides. 



Culture. Culture of Saccharomyces or Torula. 



Method. 1. Prepare and fix the film upon the slide in 

 the usual way. 



2. Soak in 3% ferric ammonium sulphate "for two hours. 



3. Wash thoroughly in water. 



4. Stain in hematoxylin solution for thirty minutes. 



5. Wash in water. 



6. Differentiate in ferric ammonium sulphate solution 

 for one and a half to two minutes, examining wet under 

 the microscope during the process. 



7. Wash, dry and mount. 



