130 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. 



Chloroiodide 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, w r hile the protoplast and connections should 

 be a blue black. 



