52 MICROSCOPIC TECHNIQUES 



3. After washing sections in distilled water, mordant for 20 rain, 

 in the tannin soln. and again wash. 



4. Stain sections in either toluidine blue, gentian violet, or 

 methyl green for 5-10 min. 



5. Differentiate in 95% alcohol, dehydrate in absolute alcohol, 

 clear in xylol, and mount in balsam. 



Result. The starch will appear as either blue, violet, or green 

 granules depending on which of the stains was used in step 4. The 

 mitochondria will appear red. 



CELLULOSE 



Post and Laudermilk (1942) Iodine Stain for Cellulose 



SPECIAL REAGENTS 



Iodine Solution. 20 ml. 2% iodine in 5% potassium iodide, 180 



ml. distilled water, and 0.5 ml. glycerol. 

 Lithium Chloride Solution. Saturate 15 ml. distilled water at 80°, 



cool; use supernatant soln. 



PROCEDURE 



1. Tease out sections or fibers. 



2. Apply 2-3 drops of the iodine soln. and after 10 sec. blot 

 with filter paper and dry. 



3. Add a drop of the lithium chloride soln., cover, and examine. 



Result. Cellulose appears in the following colors depending on 

 its source : 



Typical color Fiber 



Light blue cotton, soda pulp, bleached sulfite, straw, 



esparto 



Dark blue pineapple fiber 



Greenish blue linen 



Green to yellowish green ...sisal, Manila hemp, yucca 



Yellow yucca, ground wood, hemp, Manila hemp 



Lemon yellow kapok 



Brownish yellow \nio 



CHITIN* 



The horny carbohydrate material, chitin, requires special treat- 

 ment to soften it sufficiently for the preparation of paraffin sections. 



* See Bibliography Appendix, Ref . 16. 



