32 W. H. E M I G 



light brown in the presence of potassium dichromate. Without 

 the addition of acids the dye has slight staining properties. 



148. Tropaeolin O is an acid dye, light 3 ; J gram in 95 ml. of 

 distilled water, 1 ml. of 1 per cent sulfuric acid, and 5 ml. of ^ per 

 cent potassium dichromate. Vascular plant tissues are stained yel- 

 lowish orange to brown of moderate fastness. Blue-green algae 

 are clear yellow in alkaline solutions of the dye. 



151. Orange II, Acid Orange II, Gold Orange, Tropaeolin 

 OOO No. 2 is an acid dye, light 3 to 4 ; ^ gram in 100 ml. of dis- 

 tilled water and 1 ml. of 1 per cent sulfuric acid. 



In staining vertebrate tissues or whole mounts of invertebrates 

 use a mixture consisting of two parts Sun Yellow, C. I. No. 620, 

 and one part Orange II for five to ten minutes and counterstain 

 either in Aniline Blue, C. I. No. 707, for 15 seconds or in Niagara 

 Sky Blue, C. I. No. 520, for 30 seconds. In a combination with 

 Acid Fuchsine, C. I. No. 692, use nine parts of Orange II and one 

 part Acid Fuchsine for two minutes and follow with Niagara Sky 

 Blue for 30 seconds. If the tissue differentiates clearly, the red, 

 orange, and blue provide a striking contrast. 



On sections of animal or fungous tissues use a mixture of Sun 

 Yellow and Orange II for 10 minutes and counterstain in Niagara 

 Sky Blue. Aniline Blue may be tried as a counterstain either with 

 Orange II alone or with the mixture of Sun Yellow and Orange 

 II. A very good triple stain on plant tissues includes a mixture of 

 two parts Orange II and one part Biebrich Scarlet for 24 hours. 

 After a rinse in distilled water, counterstain meristems with 

 Niagara Sky Blue; woody tissues may be counterstained in 

 Niagara Sky Blue, Methyl Violet, C. I. No. 680, or New Methylene 

 Blue, C. I. No. 927. 



Treat mature plant tissues with \ per cent potassium dichro- 

 mate for 15 minutes, rinse in distilled water, and stain for 24 hours 

 in Orange II. The counterstains are: (1) Aldehyde Green, C. I. 

 No. 676a, five to ten minutes for blue-green and orange, (2) 

 Thionine, C. I. No. 920, for blue and orange, (3) Victoria Blue B, 

 C. I. No. 729, five minutes, (4) Methyl Violet one minute, or (5) 

 New Methylene Blue one to five minutes. 



