APPENDIX. 393 



Chloral Hydrate Carmine is useful for clearing pollen grains 

 and staining their nuclei at the same time. Add 1 gram of carmine 

 and 4 c.c. of strong hydrochloric acid to 30 c.c. of strong alcohol, 

 and warm for 15 minutes on a water-bath. After cooling, add 

 25 grams of chloral hydrate, and filter the solution until clear. 



Chloral Hydrate Iodine is used to demonstrate the presence 

 of starch in chloroplasts, or in any position where it is obscured by 

 other substances. Dissolve 5 parts of chloral hydrate in 2 of water, 

 and add enough powdered iodine to leave an excess undissolved 

 after standing for some time ; shake before iising. Bleach leaves 

 with alcohol and lay them in the solution for an hour or longer, to 

 get the best results. 



Chloroform is used as a solvent for oils, rubber particles in 

 latex, etc. ; as an anaesthetic in experiments on movements, 

 irritability, etc. ; and as an antiseptic in digestion experiments. 



Chlor zinc iodine (Chloroiodide of Zinc, Schultze's Solu- 

 tion) is one of the most useful microchernical reagents for general 

 work. It may be bought ready made, or it may be prepared as 

 follows : Dissolve 30 grams of zinc chloride, 5 grams of potassium 

 iodide, and 1 gram of iodine in 14 c.c. of water. With this reagent, 

 which should be kept in darkness, cellulose walls turn blue or violet, 

 lignified walls yellow, cutinised and suberised walls yellow or 

 brown, and proteins brown, while starch grains swell and turn blue. 



Chlorophyll Solution, prepared as directed in 247, in strong 

 alcoholic solution, may be used to demonstrate suberised and 

 cutinised walls. Place sections of stems, etc., in the chlorophyll 

 solution for an hour or so in darkness ; the corky and cutinised 

 walls are stained green, while the cellulose and lignified walls 

 remain unstained. The solution will not keep, but should be 

 freshly prepared when required. 



Chromic Acid. (1) A saturated aqueous solution is used for 

 maceration ; thin pieces of the tissue are placed in it for a minute 

 or two, then washed in water. (2) The strong solution dissolves 

 cellulose and lignified walls, cut cutinised walls resist its action. 

 (3) A 1 or 2 per cent, solution brings out the stratification of cell- 

 walls clearly. (4) A 1 per cent, solution gives a brown precipitate 

 with tannins. (5) The weak solution is used for killing and fixing 

 tissues ; the material should be well washed with water and 

 dehydrated gradually in ascending series of alcohol (30, 50, 70, 90, 

 and strong alcohol). (6) Flinty skeletons of Diatoms, flinty in- 

 crustations of Equisetum epidermis, etc., may be prepared by 

 placing the material in strong sulphuric acid until it becomes black, 

 then in 20 per cent, chromic acid for a few minutes, and washing in 

 water. 



Copper Acetate. (1) Used, with iron sulphate, in detection 

 of tannin, a brown precipitate being given. Place sections in 



