SPECIAL METHODS 147 



in clove oil, often fails, but sometimes succeeds; and, when successful, 

 the connections stand out beautifully. 



The endosperm of Phytelephas (vegetable ivory), of dates, and 

 many other pahns, and probably most hard endosperms, will show the 

 connections by the methods just described; but in many cases it is 

 necessary to resort to special methods in order to demonstrate the con- 

 tinuity. In these special methods a reagent is used which causes the 

 membranes to swell before the stain is applied. It is only by such an 

 exaggeration that the more dehcate connections can be shown. 



Put thin sections of fresh material into a mixture of equal parts 

 of sulphuric acid and water and allow the reagent to act for 2-10 sec- 

 onds. 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 acidulated 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 anihn blue. Examine 

 in glycerin. 



Try Meyer's pyoktanin method with seeds from dates as you get 

 them on the market. Remove any oils and fats with ether, transfer to 

 absolute alcohol, 95, 85, 70, 50, 35, and 20 per cent alcohol, about 5 

 minutes in each; then wash well in water and use the following re- 

 agents : 



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 solu- 

 tion, 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 



