140 
METHODS IN PLANT HISTOLOGY 
Put thin sections of fresh material into a mixture of equal parts 
of sulphuric acid and water; and allow the reagent to act for 2 to 
10 seconds. Wash the acid out thoroughly in water and stain in 
anilin blue. According to Gardiner, this stain should be made by 
adding 1 g. of the dry stain to 100 c.c. of a saturated solution of 
picric acid in 50 per cent alcohol. The staining solution is then 
washed out in water, and the sections are mounted in glycerin. The 
sections may be dehydrated, cleared in clove oil, and mounted in 
balsam. The anilin blue may be used in 50 per cent alcohol acidu¬ 
lated with a few drops of acetic acid. 
Chloro'iodide of zinc may be used instead of sulphuric acid. Treat 
the fresh sections for 2 hours with the iodine and potassium-iodide 
solution used in testing for starch; then treat about 12 hours with 
chloroiodide of zinc. Wash in water and stain in anilin blue. 
Examine in glycerin. 
Meyer’s pyoktanin method is one of the best. The reagents are 
as follows: 
1. Iodine, potassium iodide solution: iodine 1 part, potassium iodide 
1 part, water 200 parts. 
2. Sulphuric acid 1 part, water 3 parts; this mixture to be saturated 
with iodine. 
3. Pyoktanin coeruleum 1 g., water 30 c.c. This pyoktanin is a very 
pure methyl violet obtained from E. Merck in Darmstadt. 
Put sections of the date seed into a watch glass full of the first 
solution, and allow it to act for a few minutes; then mount in a drop 
of the solution. The connections will be only very faintly stained, 
showing a slightly yellowish color. At the edge of the cover, add a 
drop of the second solution. The preparation will darken a little. 
Then allow a small drop of the third solution to run under the cover. 
Allow the stain to act for about 3 minutes. Then plunge the whole 
preparation into water. The action should be stopped before 
the entire section has become blue. Now wash the section quickly. 
If there are annoying, granular precipitates, remove them with 
a soft brush. Mount in glycerin. The membrane should be a 
clear blue, while the protoplast and connections should be a blue 
black. 
The following is Strasburger’s modification of Meyer’s method, 
and shows the connections with great distinctness: 
