144 



Biological Stains 



very valuable counterstain to safranin, especially after Flemming 

 fixation, thus finding employment in cytological work. It 

 photographs well. It is a constituent, together with neutral red, 

 of the compound dye employed in the Twort (1924) stain for 

 microorganisms in tissues and has been applied to the staining of 

 bacteria, yeasts, algae, etc., under various conditions. In plant 

 histology it is a useful cytoplasm and cellulose stain and has been 

 employed by Buchholz (1931), mixed with acid fuchsin, for staining 

 pollen tubes. Its greatest drawback is that it fades rapidly and is 

 therefore not very permanent. Where greater permanency is de- 

 sired the following dye may often be substituted for it. 



PROCEDURES RECOMMENDED BY THE COMMISSION IN WHICH THIS STAIN IS USED* 



*Under this heading are given references to procedures described in detail in 

 Staining Procedures, edited by Conn and Darrow (1943-4). 



m65 



FAST GREEN FCF 



This is a dye, very closely related to light green SF yellowish, 

 which was originally proposed by Johnson and Staub (1927) as 

 a food dye. 



NaSO, 



CH3 CH, 



CH, 



.N_/- 



CH2'CHj 



/ 



/ I \CH._/— \_SO3Na 

 SO3 \_/ 



OH 



C37H34N20ioS3Na2; Mol. Wt. 808.832 



{An acid dye; absorption maxima about 625 , [420-430]) 



Solubility at 26° C: in water 16.04%; in alcohol 0.35% 



This dye was first tried in the Commission laboratory as a sub- 

 stitute for light green SF yellowish (see Haynes 1928) and has 

 now come into general use in plant histology and cytology. It 

 gives staining effects very much like light green and is consider- 



