Freehand Sections 87 



some structures the stain is more brilliant than with the simple 

 clove-oil solution. 



Sections from fresh material are fixed in 95 per cent alcohol; 

 sections from preserved material are rinsed in alcohol or water before 

 staining. The following schedule will summarize the method: 



1 Safranin, 2 to 24 hours. 



2. 50 per cent alcohol, until differentiated. 



3. Dehydrate in 95 and 100 per cent alcohol. 



4. Light green (in clove oil), 3 to 30 minutes. 



5. Xylol: 2 or 3 c.c. of absolute alcohol may be added to each 100 c.c. of 

 xylol, if the free light green shows a tendency to precipitate. 



6. Mount in balsam. 



This stain is particularly good for phloem. Since the light green 

 is not likely to overstain and does not extract the safranin, the 

 combination is a rather easy one. Even the beginner can hardly 

 fail to get a good preparation. 



Malachite Green and Congo Red. I am indebted to Dr. Sharp 

 for this method, which has been popular in Professor Gregoire's 

 laboratory at Lou vain. 



Sections of fresh material should be treated with 95 per cent 

 alcohol and then transferred to water. 



1. 3 per cent aqueous solution of malachite green or methylin blue, 

 6 hours or more. 



2. Wash in water. 



3. Congo red, 1 per cent aqueous solution, 15 minutes. 



4. Wash in water. 



5. Rinse in 80 per cent alcohol. As soon as the malachite green or anilin 

 blue color appears through the red, transfer quickly to 



6. Absolute alcohol. 



7. Xvlol. 



mt 



8. Balsam. 



Iodine Green and Acid Fuchsin is another good combination 

 for such sections. The stain will be particularly brilliant if sections 

 from fresh material are fixed in 1 per cent chromo-acetic acid for 10 

 to 24 hours; and then washed for an hour in water. Beginning 

 with the sections in water, the procedure is as follows: 



Stain in aqueous iodine green for 12 to 24 hours. Then wash in 

 water until the stain is nearly all washed out from the cellulose walls, 



