APPENDIX. 399 



drop in the tube and break it by striking the bottle on the palm of 

 the hand, then pour in the remaining 39 c.c. of water required. 

 Osmic acid should be kept in the dark in a well stoppered bottle. 



Phenol. See Carbolic Acid. 



Fhloroglucin, used as a test for lignin ( 79) and for inulin 

 ( 77) is rather expensive, but may be bought in the dilute solution 

 required ; hydrochloric acid should be added. 



Picric Acid. (1) Saturated aqueous solution of picric acid is 

 often used for fixing the cell contents, but it is difficult to wash it 

 out alcohol dissolves it better than water. (2) To demonstrate 

 the structure of protein grains, place the material in strong alco- 

 holic solution of picric acid for several hours, rinse in alcohol, and 

 stain for a few minutes in alcoholic solution of eosin. (3) The 

 chloroplasts and pyrenoids of Algae are simultaneously fixed and 

 stained by placing the material in some strong solution of picric 

 acid in 50 per cent, alcohol, to which has been added some acid 

 fuchsin solution. 



Picric Aniline Blue. For a rapid differentiating stain, add 

 aniline blue to saturated picric acid solution in 50 per cent, alcohol, 

 until the solution becomes blue-green. This mixture will stain 

 cellulose walls and cell contents blue, while the lignified walls are 

 stained yellow. 



Pier o nigrosin is used for (1) simultaneous fixing and staining 

 of delicate tissues ; (2) staining leucoplasts and nuclei ; (3) double 

 staining modified and unmodified cell-walls ; and (4) is especially 

 good for filamentous Algae and Fungi. Dissolve nigrosin in concen- 

 trated aqueous or alcoholic solution of picric acid. The solution 

 will need to act for 3 or 4 hours, or overnight. The alcoholic solu- 

 tion is best for material containing chlorophyll, which will be 

 extracted by alcohol. Nuclei and leucoplasts are stained steel-blue 

 by the nigrosin. 



Potash (Caustic Potash). For general use, dissolve 5 grams 

 of stick potash in 95 c.c. of water. This solution serves (1) as a 

 clearing agent after clearing, the potash should be washed out with 

 water and neutralised by adding some acetic acid ; (2) to cause 

 swelling of cell-walls and starch grains ; (3) to dissolve inulin 

 crystals, protein crystals, and most protein grains ; (4) to saponify 

 oils ; (5) to make tannin-containing cells red. Strong solution (50 

 per cent, is used as (6) a test for suberin ; (7) a maceration fluid 

 boil the tissue in the solution for a few minutes, then pour into 

 water, tease with needles, and mount in glycerine, adding acetic 

 acid if the isolated cells are too transparent. 



Potash, Acetate of. Strong solution in water is used for 

 mounting preparations of green tissues, green Algae, etc., since in 

 this solution they keep their green colour for a long time. 



