SECTION THREE 



14. Dehydrate as usual. 



15. Immerse for five minutes in equal parts of absolute alcohol 

 and xylol. 



16. Transfer to and immerse in xylol for five minutes. 



17. Mount in Canada balsam in xylol. 



Results: 



Chromosomes, black to purple. Centrosomes and pyrenoids, 

 black to purple. Lignified, suberized and cutinized structures, un- 

 stained or only faintly stained. Archesporial cells and early stages 

 of sporogenous tissue, grey. 



IODINE GREEN - ACID FUCHSIN 

 A botanical stain for lignified tissues, and for chromosomes 



Solutions required: 



A. Iodine 1% aqueous. 



B. Acid fuchsin 1% aqueous. 



Technique: 



1 . Fix material in Nevashin's fluid. 



2. Take sections through to distilled water in the usual manner. 



3. Immerse for at least twelve hours in the Iodine green 

 solution. 



4. Wash and differentiate with distilled water, examining at 

 intervals under the microscope while the preparation is still wet, 

 until the non-lignified tissues retain only a faint green tint. 



5. Counterstain for about fiYQ minutes in the acid fuchsin 

 solution, controlling by examination under the microscope, while 

 the preparation is still wet, taking care to ensure that the acid 

 fuchsin solution is not allowed to act long enough to extract the 

 Iodine green from the lignified tissues. 



6. Rinse quickly in 90% alcohol. 



7. Dehydrate quickly in two changes of absolute alcohol. 



8. Clear in clove oil. 



9. Wash with xylol. 



261 



