20 W. H. E M I G 



Cleared sections are covered with a drop of balsam 

 and a dry cover glass is added. 

 II. Two dye-solutions mixed. 



1 . Five minutes in a mixture of ten parts Crocein Scarlet 

 MOO and one part Niagara Sky Blue. 



2. Rinse the material in distilled water. 



3. Follow the instructions given in the previous outline 

 schedule beginning with dehydration. 



Example No. 2 — Sun Yellow, C. I. No. 620, and New Methylene 



Blue, C. I. No. 927. 

 This combination of a direct yellow and a basic blue dye is 

 especially useful on plant tissues; it may be tried on invertebrate 

 animals. 



1 . The material is given 24 hours in Sun Yellow. 



2. Rinse the objects in distilled water. 



3. Counterstain in New Methylene Blue, five minutes. 



4. Rinse the material in distilled water. 



5. Follow the usual laboratory procedure beginning with 

 dehydration. 



The two dyes cannot be mixed because a precipitate forms 

 as soon as the stains are combined. The length of time the tissue 

 remains in New Methylene Blue modifies the results giving either 

 yellow and green, green and blue, or the three colors, yellow, green, 

 and blue. 



Example No. 3 — Rhodamine 6G, C. I. No. 752, and Aniline Blue, 



C. I. No. 707. 



In staining mature vascular plants, the tissues are left for 24 

 hours in Rhodamine 6G, a bright red basic dye that does not over- 

 stain. The principal problem of technique at this stage is the 

 addition of enough Aniline Blue so that the red and blue are of 

 equal density. Use Aniline Blue on one stem section for a minute, 

 on another for two minutes, and on a third for five minutes. These 

 three sections in xylene serve as a comparison in determining the 

 correct time interval to be used. 



If a counterstain covers all of the first color within a few sec- 

 onds, the counterstain is too intense. Under this circumstance, a 



