GLYCOGEN, MUCIN, AND STARCH 51 



pleted when the glycogen 'and mucin appear deep brown or black. 

 The background will be yellowish. Usually 1-3 hr. is required. 



6. Rinse well in repeated changes of distilled water and tone in 

 the gold chloride soln. for 5 min. 



7. Rinse in distilled water and then in the hyposulfite soln. to 

 remove unreacted silver. 



8. Wash in tap water and counterstain if desired. 



9. Mount as usual. 



Result. Glycogen and mucin will appear in shades from grey- 

 brown to black on an unstained background. Sometimes the collodion 

 film becomes stained and it can be removed by acetone or alcohol- 

 ether. 



STARCH 



The common practice of employing a dilute iodine solution to 

 develop a blue color with starch can be applied to sections of plant 

 material, as can the crystal violet stain followed by washing with 

 saturated picric acid solution. The use of formaldehyde as a swelling 

 agent to obtain special effects with safranine and fast green 

 FCF was described by Bates (1942). Starch granules can also be 

 recognized by the characteristic black crosses they exhibit due to 

 their doubly refractive pioperties when viewed under the micro- 

 scope with polarized light. 



The following procedure of Milovidov (1928) is well suited for 

 the preparation of permanently mounted sections stained for starch. 



Milovidov Method for Starch 



SPECIAL REAGENTS 



Aniline Fuchsin Stain. 



5% Alcoholic Aurantia. 



2% Tannin. 



1 % Toluidine Blue, Gentian Violet, or Methyl Green. 



PROCEDURE 



1. Fix plant tissue in Regaud fluid and prepare sections as usual. 



2. Stain sections with aniline fuchsin for 5 min. and differentiate 

 in the aurantia soln. 



