38 W. H. E M I G 



the stain containing acetic acid. These results indicate that the 

 dye is relatively inactive at room temperature. If the material is 

 mordanted in ferric ammonium sulfate and stained for three hours 

 at 50° C.j meristems are clear blue; brown and red algae are dark 

 blue. Nuclei become darker than the cytoplasm. In alkaline solu- 

 tions of the dye, blue-green algae stain a clear brilliant blue but the 

 color disappears in glycerin. 



Sections of animal tissues are placed in the mordant 1 per cent 

 ferric alum for 15 minutes. After a rinse in distilled water, Tolyl 

 Blue 5R stains the material at 50° C. within five to ten minutes. 

 The sections are clear bright blue. 



315. Wool Black B is an acid dye, light 3 to 4. Parenchyma 

 stains a clear blue; sclerenchyma is tinted green to dull greenish 

 black. In the presence of potassium dichromate, nuclei remain 

 uncolored but the cytoplasm stains blue-green. 



326. Direct Fast Orange, Erie Fast Orange (NAC), Erie 

 Fast Scarlet YA (NAC) is a direct dye, light 3. 



327. Direct Fast Scarlet 4BS, Pontamine Fast Scarlet 4BS 

 (Du Pont) is a direct dye, light 3; J gram in 95 ml. of distilled 

 water, 5 ml. of 5 per cent sodium sulfate, and \ ml. of acetic acid. 

 Direct Fast Orange and Direct Fast Scarlet differ only in color. 

 The two dyes are not so good on tissues taken from Gilson's or 

 Bouin's fixative. Whenever alcohol, formalin, and acetic acid are 

 used in one of the many modifications of fixatives, animal tissues 

 become brilliant orange-red in 15 to 30 minutes, but mature plant 

 tissues need an overnight stain for a full development of the color. 

 Fortunately, the dye does not overstain. It is fast to washing in 

 water, alcohol, ferric alum, and remarkably fast to acids, including 

 nitric acid. 



Direct Fast Scarlet 4BS may be used as a general stain instead 

 of Carmine on paraffin sections of animal or fungous tissues. The 

 dye is most useful as a counterstain. The material is first stained 

 in iron Haematoxylin, differentiated in iron alum, and then 

 counterstained in Direct Fast Scarlet 4BS — animal tissues 15 to 30 

 minutes, meristematic plant tissues 30 minutes, mature plant 

 tissues overnight. The differential staining of parasitic fungi and 



