DOUBLE-STAINED HAND SECTION OF ROOT 107 



alcohol for the removal of the xylene, and thence graded down through alco- 

 hols to water. By whatever method the sections are produced, they are accumu- 

 lated in a small dish of distilled water. These sections, of course, will retain 

 the cell contents, which must be removed in order that the sections may be 

 turned into true skeletons. 



The best reagent to use for skeletonizing sections of plant tissue, is either 

 potassium or sodium hypochlorite. Ordinary "bleaching solutions" sold for 

 household purposes under various trade names are not suitable since they con- 

 tain large quantities of calcium hypochlorite. If, however, the pure salts are 

 not available, the household solution may be employed by adding to it enough 

 of a solution of potassium or sodium carbonate to precipitate the calcareous con- 

 tents and by filtering off the solution before use. If the pure salts are available, a 

 1 per cent solution may be employed conveniently. The sections are removed 

 from the distilled water on a section lifter and transferred to a watch glass of the 

 sodium or potassium hypochlorite solution. If the sections are made from mate- 

 rial which has been preserved in alcohol, this solution should be used cold, but 

 usually it must be warmed if it is to have the desired effect on materials which 

 have been resurrected from a dried condition. In either case the operation should 

 be watched very carefully under a low power of the microscope, and the action of 

 the hypochlorite should be discontinued as soon as the cells are seen to be free of 

 their contents. If the mounter is completely inexperienced in this field and is un- 

 able to determine the point at which the operation should be stopped, it is rec- 

 ommended that a single section be taken and the skeletonizing followed under 

 a microscope while it is timed. It will be seen that when the operation has 

 gone too far the finer cell walls present will be dissolved by the solution. If 

 the period at which the first of the cell walls dissolves is carefully recorded 

 and one half of this time taken for the subsequent sections, these will be cleaned 

 perfectly without the slightest risk of damage to their walls. After they are 

 removed from the hypochlorite solution, the sections should be washed thor- 

 oughly in several changes of distilled water and then passed into a solution of 

 1 per cent acetic acid. Here they are rinsed several times and then rewashed 

 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 which is 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 



