396 APPENDIX. 



iodine, and cut sections ; place these in fuchsin for 24 hours, rinse 

 in water, and mount in glycerine. 



Glycerine, used for mounting, may be applied either pure or 

 diluted with equal volume of water. See 15. 



Glycerine Jelly, used for mounting, may be bought ready 

 prepared. See 16. 



Haematoxylin, Delafield's. This is perhaps the best general 

 stain. It may be bought ready made up, or may be prepared as 

 follows : Mix 4 c.c. of saturated alcoholic solution of haermitoxylin 

 crystals with 150 c.c. of saturated aqueous solution of ammonia 

 alum crystals. Let stand for a week exposed to light, filter, and 

 mix the filtrate with 25 c.c. of glycerine and 25 c.c. of methylated 

 alcohol. Let stand for a few hours, filter off any precipitate, and 

 keep in a tightly stoppered bottle. Precipitates are sometimes 

 formed in specimens stained with haematoxylin, but these can be 

 removed by rinsing with acid alcohol (5 drops of hydrochloric acid 

 to 100 c.c. of alcohol) ; then treat with strong alcohol, and with 

 clove oil or xylol, and mount in balsam. A gcod double stain is 

 given if sections are placed in safranin for at least half an hour, 

 washed in water, and placed for a minute or two in haematoxylin ; 

 lignified and suberised walls are stained red, cellulose walls purple. 



Hoffmann's Blue is used in solution in 50 per cent, alcohol, 

 with addition of a little acetic acid. (1) It stains the protoplasmic 

 cell contents and not the cell walls. (2) It stains the callus of 

 sieve- tubes. (3) To show the continuity of protoplasm through 

 pores in the walls, dissolve some dry Hoffmann's blue in strong 

 sulphuric acid, place sections in this solution for about 15 minutes, 

 then wash with water, and mount in glycerine. 



Hydrochloric Acid has many uses, mostly in conjunction with 

 other reagents. By itself, it turns lignified walls yellow. 



Indian Ink. The gelatinous sheaths of various Algae (e.g. 

 Spirogyra and other Conjugatae) may be shown up well by placing 

 the Alga in water containing Indian ink. 



Iodine has various applications in plant histology and micro- 

 chemistry. Iodine solutions may lie prepared in various ways. 



(a) Dilute iodine tincture with 5 to 1 times its volume of water. 



(b) Dissolve 1 gram of potassium iodide in a little water, dissolve 

 crystals of iodine in this until a brown colour is given, and dilute 

 with water. A rather pale solution is sufficient to colour starch 

 blue ; to stain proteins and cell-walls, a stronger solution is 

 required, (c) A mixture of equal parts of potassium-iodide iodine 

 solution and glycerine often gives good results ; the glycerine keeps 

 the preparation from drying and also acts as a clearing agent. 

 (d) To make phosphoric acid iodine, which stains cellulose violet, 

 dissolve 1 gram of potassium iodide and 1 gram of iodine in 50 c.c. 

 of strong aqueous solution of phosphoric acid. 



