212 Specific Examples of Slide Making 



washed in ordinary water until the wash water no longer smells of the 

 acetic acid. The skeletonized sections from as many roots as it is desired 

 to cut at one time should be accumulated in water until one is ready to 

 stain them, or they may be preserved indefinitely in 90 per cent alcohol. 



The stain recommended in the present case is freshly prepared for use 

 by mixing equal parts of a 0.2 per cent acid fuchsin solution and a 0.2 per 

 cent iodine green solution. The mixed stains do not remain usable for 

 much longer than one day, but the two separate stock solutions may be 

 kept for an indefinite period. The differentiating solution, which is 1 per 

 cent acetic acid in absolute alcohol containing 0.1 per cent iodine, is also 

 stable. The staining solution should be placed in a small corked vial or 

 stoppered bottle and the sections transferred to it from the water. They 

 should remain in stain for about 24 hr. It is recommended that they 

 should not be left longer than 36 hr because they may suffer from a 

 precipitate over the surface, and when the staining period is concluded 

 the contents of the vial should be tipped out into a large watch glass. It 

 will usually be found that some of the sections remain behind, stuck to 

 the side of the vial from which they are removed. Under no circumstances 

 should the vial be rinsed with anything except the staining solution, 

 which should be poured back from the watch glass ( the sections will have 

 settled to the bottom ) , swirled around, and returned to the watch glass. 

 In this way in a short time all the sections may be removed from the vial 

 to the watch glass. In a second watch glass or even a small crystallizing 

 dish is placed an adequate quantity of the differentiating solution. Each 

 section is removed individually with a section lifter from the stain and 

 placed into the differentiating solution, where it may be watched under 

 the low power of a microscope as the dish is rocked gently from side to 

 side. Differentiation will usually take place within 2 or 3 min and may be 

 determined without the least difficulty when the lignified tissues are found 

 to be of a bright clear green, leaving a bright red in the nonlignified 

 tissues. This process of differentiation is also one of dehydration, so that 

 the sections may now be removed with a section lifter from the differenti- 

 ating solution and placed in a clearing agent. The author's preference is 

 for terpineol, which has all the advantages of clove oil without the dis- 

 advantage of making the sections brittle so that they crack on mounting. 

 All the sections may be passed through the differentiating solution and 

 accumulated in terpineol. They may remain in terpineol until removed 

 to a slide, where they are covered with balsam and mounted in the 

 normal manner. 



Sections prepared in this manner are permanent, and the process is so 

 simple that it can be recommended most warmly as an introduction to 

 plant-section-staining techniques for an elementary class. The sections, 

 however, are differentiated clearly enough to be used for instructing a 



