GENERAL STAINING 653 



Methyl green or iodine green may be used in place of the light 

 green. It is less easy to obtain a clear green colour with them 

 and they are less permanent. Parenchyma containing tannin 

 frequently holds the green stain well. The combination is unsuit- 

 able for tissues weakly lignified, 



A violet staining of the cellulose tissues is obtainable using an 

 aqueous, alcoholic or clove oil solution of crystal or gentian violet 

 in place of the light green, and an orange stain by the use of 

 oranffc G. in cither alcohol or clove oil solution. 



1295. Safranin and Anilin Blue. Stain in safranin and 

 partially differentiate. Stain in alcoholic anilin blue one to ten 

 minutes and differentiate briefly in 95 per cent, alcohol. Then 

 fix and intensify the blue stain with slightly acidulated (HCl) 

 alcohol. Wash in neutral 95 per cent, alcohol, followed by 

 absolute, and clear in xylol. The cellulose tissues stain a brilliant 

 blue. The combination is difficult and the contrast unsuitable for 

 microphotography. 



The use of auramine in place of the safranin gives an easier 

 combination and a less severe contrast. 



1296. Crystal (or Gentian) Violet and Bismark Brown. Stain in 

 aqueous violet solution ten to twenty minutes, and without 

 washing stain in Bismark brown (in 80 per cent, alcohol) for about 

 five seconds. Dehydrate rapidly in absolute alcohol and differ- 

 entiate in clove oil. Wash in xylol. A brilliant stain : lignified 

 tissues, cuticle and cork violet, cellulose tissues brown. 



Orange G, in alcoholic or clove oil solution, may be used in 

 place of the Bismark brown to give an orange stain in the cellulose 

 tissues. 



Warington {Ann. Bot., xl, 1926, p. 27) uses gentian violet 

 (saturated solution in 40 per cent, alcohol) for ten minutes, followed 

 by Vesuvian brown (saturated solution in 50 per cent, alcohol) for 

 a few seconds. 



1297. Iodine Green and Acid Fuchsin. Stain in aqueous iodine 

 green and differentiate briefly with 95 per cent, alcohol. Counter- 

 stain with acid fuchsin for two to three minutes. Differentiate 

 in absolute alcohol. Lignified tissues, cuticle and cork green, 

 cellulose tissues pink. The difficulty lies in losing too much green, 

 but the combination is useful in giving green xylem where the 

 latter is too dense to photograph when red. The stock solution 

 of acid fuchsin is often best diluted with 1 to 5 parts of 70 per 

 cent, alcohol. Methyl green (aqueous solution) can be used in 

 place of iodine green. 



1298. Bismark Brown and Light Green. Stain lightly with 

 Bismark brown and differentiate in 50 per cent, alcohol. Counter- 

 stain with alcoholic light green for one to five minutes and 

 differentiate in 70 per cent, alcohol. Lignified tissues brown, 

 cellulose green. Differentiation not always very sharp. 



