DETECTION OF SUBER1N, ETC. 165 



phate, thallin sulphate, phloroglucin and the other reagents 

 mentioned in paragraph 7, are due to the presence of a 

 furfural-yielding complex in the lignin ; any substance in the 

 plant which contains this complex, e.g. coniferin, will give 

 similar reactions. 



9. If lignified tissues be treated with chlorine water and 

 then with sodium sulphide, a deep magenta colour is produced. 



10. Lignocelluloses induce the formation of Prussian blue 

 in the greenish-red solution produced by mixing ferric chlo- 

 ride with potassium ferricyanide. 



(b) Suberin and Cutin. 



1. With chlorzinc iodide, and also with iodine and sul- 

 phuric acid, a brown or yellow colour is given. 



2. Suberized and cuticularized walls are insoluble in 

 cuprammonia and concentrated sulphuric acid. 



3. Suberized walls are coloured yellow with strong potash 

 solution; on heating the colour deepens, and on boiling 

 yellow oily drops exude from the membranes. 



4. Suberized walls are the most resistant of membranes to 

 Schultze's macerating mixture ; but on boiling, oily drops of 

 eerie acid are formed which are insoluble in carbon bisulphide 

 but soluble in ether, benzol, and hot alcohol. 



5. Suberized and cuticularized walls are stained green by 

 the action of alcoholic solutions of chlorophyll. A strong 

 fresh solution of chlorophyll must be used, and the treatment 

 should last for at least fifteen minutes in the dark. The 

 sections may be washed in and examined in water. (Lig- 

 nified walls are unacted upon by this and the following 

 reagents.) 



6. Similarly the same membranes are stained red by treat- 

 ment with alcoholic solutions of Alkannin, Sudan III and 

 Scharlach R. 



7. If a section of the material be treated first with eau de 

 Javelle, in order to destroy any tannins which may be present, 

 suberized walls are stained very deeply with a solution of 

 cyanin in 50 per cent alcohol to which an equal volume of 

 glycerin has been added. Lignified walls will not be stained 

 owing to the preliminary treatment with the eau de Javelle. 



8. Corky walls are stained orange-yellow by an alcoholic 



