46 
METHODS IN PLANT HISTOLOGY 
7. Wash in water, 5 minutes. 
The water should be changed several times. If the washing is not 
thorough, the differentiation will not be sharp. 
8. Haematoxylin. 
Many objects, like the archegonia of gymnosperms and the embryo 
sacs of angiosperms, will stain sufficiently in 5 or 6 hours; most algae 
require at least 20 hours. 
9. Wash in water, 5 minutes, changing as often as the water shows any color. 
10. Iron-alum, 2 per cent solution. 
No time can be indicated here. The preparation must be watched 
under the microscope. After some experience, on'e can form some 
judgment from the color tone, as the slide stands in the Stender dish 
of iron-alum, but the finishing must always be done under the microscope. 
If the stain is coming out rather slowly, as it should, one can handle 
6 to 10 slides at one time. Put the slides on a 5X7 glass plate and put 
the plate on the stage of the microscope. The iron-alum can be added 
or removed with a pipette. As slide after slide reaches the proper 
differentiation, it is placed in water. 
11. Water, 30 minutes. 
The water should be changed several times. If this washing is 
not thorough, the preparation will fade, on account of the continued 
action of the iron-alum. If an aqueous counter-stain is used, apply it 
at this point. 
12. 35, 50, 70, 85, 95, 100 per cent alcohol, 5 minutes in each. 
If an alcoholic counter-stain is used, apply it near the alcohol of 
the same strength as the stain. 
13. Absolute alcohol and xylol, equal parts, 5 minutes. 
14. Xylol, 2 to 5 minutes. 
15. Balsam. 
Sharp’s Schedule.— 
1. Remove the paraffin with xylol. 
2. Rinse in absolute alcohol. 
3. 95 per cent alcohol. 
4. 50 per cent alcohol. 
5. Water. 
6. If osmic acid has been used in fixing, place the slides in 10 per cent 
solution of peroxide of hydrogen in water until bleached. 
7. Water. 
8. Iron-alum, 2§ per cent, 2 to 3 hours. 
9. Wash well. 
10. ^ per cent haematoxylin, 24 hours. 
11. Wash in water. 
