506 PRACTICAL BOTANY 



56 c.c. of distilled water ; to this 1 gramme of carmine is added, 

 and then twice its volume of absolute alcohol is added to the 

 liquid. After nitration the liquid is ready for use. 



Carmine has but little differentiating power : it readily stains 

 the protoplasm and the nucleus ; Thiersch's preparation is espe- 

 cially useful for bringing out the structure of the nucleus. It can 

 very well be used for sections which have been previously treated 

 with picric, chromic, and osmic acids. The time during which 

 the section is to be exposed to its action varies very much ; 

 the rule is that the most satisfactory results are obtained by 

 a prolonged immersion in a dilute solution. In case of over- 

 staining, the section may be washed for a moment in water to 

 which a trace of ammonia has been added. 



Preparations stained with carmine are best mounted in glycerine. 

 (See also Picro-carmine.) 



Chloral Hydrate is used, together with iodine, for the detection 

 of starch-grains included in the chlorophyll-corpuscles. Dissolve 

 8 parts chloral hydrate in 5 parts of water, and add crystals of 

 iodine, which will dissolve slowly and colour the solution. The 

 material to be tested should be bleached with alcohol, and then 

 be laid in the solution for twelve to twenty-four hours (see pp. 

 46, 130). 



Chloroform is used as a solvent for various substances, e.g. 

 oils, coag ulum of latex, &c. 



Chlor-Zinc-Iodine (Schulze's Solution) is the best differen- 

 tiating reagent, and the one most generally used, but the chief 

 objection to it is that, as in the case of other preparations of iodine, 

 the stain in not permanent. There are various ways of preparing 

 it, but the best is as follows : 



1. Dissolve 110 grammes of zinc in 300 c.c. of pure hydrochloric 

 acid, and evaporate to 150 c.c. (sp. gr. 1'8). 



2. Dissolve 12 grains of potassium iodide in as little water as 

 possible, and add 0*15 grammes of crystals of iodine. 



3. Mix (1) and (2). 



This reagent may however be obtained ready prepared from 

 dealers in microscopic requisites. It may be used either for fresh 

 material, or after treatment with picric acid, or alcohol : the 

 colouring of cellulose walls is intensified if the objects have been 



