STAINS AND STAINING 65 



This stain can be recommended for cellulose walls, achromatic 

 structures of mitotic figures, for cilia, and it is particularly valuable for 

 algae. Directions for using it with algae are given in chapter viii. 



Orange G. — Make a 1 per cent solution in water, in 95 per cent al- 

 cohol, or a j\ per cent solution in clove oil. We prefer the solution in 

 clove oil. 



The orange dissolves very slowly if put directly into clove oil. It is 

 better to dissolve | gram of orange in 50 c.c. of absolute alcohol. In a 

 well-corked bottle in the paraffin oven at 52° C, this much orange may 

 go into solution. Then remove the cork and allow about half of the 

 alcohol to evaporate. Pour on 200 c.c. or more of clove oil and let it 

 stand for several hours. If any of the stain has not gone into solution, 

 pour off the clear fluid, which is now ready for use, and pour some more 

 clove oil on the residue, allowing the residue to go slowly into solution. 

 In staining, we use a small bottle of the orange, pouring it on the slide 

 and draining it back into the bottle. The absolute alcohol, carried into 

 the clove oil in this way, does no damage, except that it dilutes the 

 stain a little. 



Transfer to the aqueous stain from water; to the alcoholic stain 

 from 85 per cent alcohol, since the stain is always applied as a second 

 or third stain ; use the solution in clove oil after the dehydration in abso- 

 lute alcohol. Times are always short and are to be reckoned in sec- 

 onds rather than in minutes. If the solution in clove oil has been used, 

 the slide should be transferred to xylol before mounting in balsam. 



This is a plasma stain. It is distinctly a general rather than a selec- 

 tive stain, but is valuable as a background for other structures which 

 have been stained violet or blue or green. It first came into prominence 

 as the third member of the triple stain — safranin, gentian violet, 

 orange. 



Gold orange. — This stain, which many incorrectly suppose to be the 

 same as orange G, is much more readily soluble in clove oil and stains 

 with much greater rapidity. 



DOUBLE STAINS AND TRIPLE STAINS 



Occasionally one uses a single stain to bring out some particular 

 structure, but in most cases two, or even three, stains are used. 



In staining a vascular bundle, one stain may be selected which stains 

 the xylem, but not the phloem, while another of a different color stains 

 the phloem, but not the xylem, thus affording a sharp contrast. In 



