BLEACHING SECTIONS. 243 



it discharges the natural colour, considerably abridges 

 the process. It has a further advantage, as the cell- 

 contents, starch, chlorophyll granules, &c., are pre- 

 served intact, and the nucleus, when it exists, is ren- 

 dered more palpable by staining. 



When the stem is hard and brown, a solution of 

 chloride of lime should be used. A quarter of an 

 ounce of chloride dissolved in a pint of water, well 

 shaken and stood by to settle down, then pour off the 

 clear fluid for use. For hard tissues this solution 

 answers well, but it is not suitable for leaves, as they 

 require not only bleaching, but the cell-contents should 

 be dissolved out to render them transparent. A solu- 

 tion of chlorinated soda answers well for both stems 

 and leaves. It is prepared as follows : 



To one pint of water add two ounces of fresh 

 chloride of lime, shake or stir it well two or three 

 times, then allow it to stand till the lime has settled. 

 Prepare meanwhile a saturated solution of carbonate 

 of soda common washing soda. Now pour off the 

 clear supernatant fluid from the chloride of lime, and 

 add to it, by degrees, the soda solution, when a preci- 

 pitate of carbonate of lime will be thrown down ; con- 

 tinue to add the soda solution till no further precipitate 

 is formed. Filter the solution, and keep it in a well- 

 stoppered bottle in the dark, otherwise it speedily 

 spoils. 



Sections bleached in chlorinated soda must, when 

 white enough, be washed in distilled water and allowed 

 to remain in it for twenty-four hours, changing the 

 water four or five times, and adding a few drops of 

 nitric acid, or at the rate of eight or ten drops to the 

 half-pint, to the w r ater employed before the final wash- 

 ing takes place. From water transfer them to alcohol, 

 in which they must remain for an hour or more. 



Sections may be stained in two colours, either by 

 alternate or single immersions. 



The first process is as follows : Transfer the section 

 from alcohol to magenta dye for about twenty minutes, 

 then remove and soak in alcohol till the colour is re- 

 moved from the parenchyma ; next place it about a 

 B 2 



