STAIN TECHNIQUE 53 



Class XL Xanthene Colouring Matters 



The majority of the Xanthene dyes are characterized by the 

 strong fluorescence of their solution which is attributed to the pres- 

 ence of the pyrone ring in the dye molecule. 



739. Pyronine 2G is a basic dye, light 1 to 2 ; £ gram in 95 ml. 

 of distilled water, 5 ml. of 5 per cent ammonium alum, and \ ml. of 

 acetic acid. Plant tissues are stained a bright red to fuchsia. The 

 color is similar to that of Basic Fuchsine, C. I. No. 677, but Pyro- 

 nine 2G is more easily differentiated in double staining than Basic 

 Fuchsine. The best contrast is obtained with either Niagara Sky 

 Blue, C. I. No. 520, or alum Haematoxylin. For staining yeast 

 spores or bacteria use 5 per cent of the dye instead of the ^ gram 

 in the regular formula. A film of yeast containing spores is dried 

 on a slide, left in 5 per cent chromic acid for 30 minutes, rinsed with 

 distilled water, stained in Pyronine 2G at 50° C. for one hour, and 

 counterstained in Niagara Sky Blue for five minutes. 



740. Acridine Red is a basic dye, light 2 ; ^ gram in 95 ml. of 

 distilled water, 5 ml. of 5 per cent ammonium alum, and J ml. of 

 acetic acid. Plant tissues are pink to bright red. It may be used 

 in any technique where Safranine, C. I. No. 841, gives good results 

 but the color will be brighter than that of Safranine. A section 

 taken from this stain may be counterstained in Aniline Blue, C. I. 

 No. 707, Niagara Sky Blue, C. I. No. 520, or alum Haematoxylin, 

 C. I. No. 1246. 



741. Pyronine B is a basic dye with properties similar to those 

 of Pyronine 2G; it is more bluish red. 



749. Rhodamine B, 750. Rhodamine G, and 752. Rhoda- 

 mine 6G are basic dyes, light 2 ; ^ gram in 95 ml. of distilled water, 

 5 ml. of 5 per cent ammonium sulfate, and J ml. of acetic acid. 

 Rhodamine 6G is a bright pink ; it is more easily differentiated with 

 blue acid or direct dyes than any other red basic stain. Rhodamine 

 6G for 12 to 24 hours does not overstain paraffin sections, freehand 

 sections of vascular plants, or woody materials. The counterstains 

 include: (1) Aniline Blue, C. I. No. 707, five minutes, (2) Niagara 

 Sky Blue, C. I. No. 520, five minutes for red and light blue, or (3) 

 alum Haematoxylin, C. I. No. 1246, for bright red and purple. 



