102 VEGETABLE HISTOLOGY. 



IODINE-GREEN. A deep green aqueous solution is used. It 

 acts like methyl-green. It is much employed along with car- 

 mine, fuchsin or eosin for double staining of tissues. The 

 stains are better used successively than mixed together. 



EOSIN. Oil of cloves solution of eosin is used for clearing 

 and at the same time staining sections that have previously been 

 treated with gentian-violet, iodine-green or methyl-green. The 

 violet or green goes to the lignified and cutinized tissues, while 

 the cellulose walls are stained red by the eosin. 



PICRO-NIGROSIN SOLUTION. Add enough of a strong aqueous 

 solution of nigrosin to a saturated solution of picric acid in 

 water to produce a deep olive-green color. This is a good 

 nuclear stain and a good double stain, the nigrosin going to the 

 cellulose and the picric acid to the lignified tissues. A compara- 

 tively long time is required for staining. 



TEMPORARY STAINS. 



POTASSIUM IODIDE-IODINE. Dissolve 1 part of iodine and 4 

 parts of potassium iodide in 10 cc. of water, then dilute with 185 

 parts of water. It is one of the most useful stains. It colors 

 starch blue, protoplasm and proteids yellowish-brown, lignifled 

 cell-walls deep brown; together with sulphuric acid it stains 

 cellulose blue. 



CHLOR-ZINC-IODINE. Dissolve 10 grams of potassium iodide 

 and 0.15 gram of iodine in 10 cc. of water. Add this solution to 

 100 grams of a solution of zinc chloride of specific gravity 1.8 

 and mix thoroughly. This reagent may be used either on fresh 

 or alcoholic material, and the specimen on the slide should be 

 nearly dried before applying it. Cellulose is colored (often 

 slowly) blue or violet, lignified walls yellow, cork yellow to 

 brown, protoplasm brown, and starch swells and is colored blue. 



PHLOROGLUCIN. A solution of 1 gram in 100 cc. of 90 per 

 cent, alcohol. The solution in time turns dark and should not 

 be kept more than three or four months. The section is first 

 immersed in the reagent, say for five minutes, after which it is 

 nearly dried and a drop of strong hydrochloric acid added to it. 

 Only lignified substance is colored. The color varies from pale 

 to dark red, according to the amount of lignification. 



ANILINE HYDROCHLORIDE. A 5 per cent, alcoholic solution is 

 employed in the same way as phloroglucin, with hydrochloric 

 acid, as a test for lignified tissues, which it stains a deep yellow. 

 It is not as good a stain as phloroglucin. 



CYANIN. A solution of cyanin in equal parts of alcohol and 

 water is used to test for fats, which are colored a beautiful blue 

 after one-half hour's immersion. Glycerin may be used to 

 wash out the superfluous stain. 



