STAINING CELLULOSE. 53 



Staining with Aniline Dyes. Methyl Green, Methylene 

 Blue, Safranine and Fuehsine give good results. Place sec- 

 tions in J p. c. solutions of either of these for 3 or 4 minutes, 

 rinse in Water, dehydrate, clear, and mount. 



Lignified Cellulose. When the cellulose undergoes the 

 change known as lignification, its reactions are altered. 

 It is coloured (i.) yellow or yellowish-brown by Chlorzinc 

 Iodine ; (ii.) red with Phloroglucin followed by Hydrochloric 

 Acid ; (iii.) yellow with Aniline Chloride. The results with 

 Phloroglucin are more definite and reliable than with Chloride 

 of Aniline. 



It is generally stated that Haematoxylin and Carmine do 

 not stain lignified tissue. With Carmine this is practically 

 true; but while it is probable that pure "Lignin" is un- 

 affected by Hsematoxylin, the tissue generally takes on a 

 modified stain, which is lighter in proportion to the extent of 

 the lignification. In young stems it is sometimes noticed that 

 Hsematoxylin has a special staining power for the " middle 

 lamella " both of wood and bast, which Carmine, on the other 

 hand, does not affect at all. 



The Aniline Dyes mentioned under " Cellulose Staining" 

 will also stain equally well lignified tissues. 



It is stained by Picric Acid, but the dye washes out easily 

 in Water or Alcohol. Good results however can be obtained 

 by carefu treatment. 



DOUBLE STAINING MIXED TISSUES. 



The most striking results are obtained by using Carmine 

 and Methyl Green. The staining with Carmine and Picric 

 Acid is also very effective, but as the Picric washes out very 

 rapidly, the sections should not remain in the Alcohol longer 

 than is required to dehydrate them. A thick section takes 



