84 BOTANICAL MICROTECHNIQUE. 



II. AROMATIC SERIES, 

 i. Phenols. 



a. Eugenol, C e H 3 .OH.OCH 3 .C 3 H 5 . 



131. Molisch (I, 40 and 44) recommends caustic potash for 

 recognizing eugenol, which occurs in the oils of pimento and 

 clove ; and he places the sections in a completely saturated 

 solution of potassium hydroxide. There are then formed in 

 a short time (about five minutes), from each oil-drop, numer- 

 ous, often very long, columnar or needle-shaped, colorless 

 crystals of potassium caryophyllate. Sections of cloves are 

 especially recommended as suitable objects for their study. 



The reactions with concentrated sulphuric or nitric acid 

 are less trustworthy. The former first colors eugenol yellow- 

 ish and then at once deep blue, with a tint of violet after a 

 time, and finally brown. The latter colors it brilliant orange 

 or brown-red. 



b. Phloroglucin, C 6 H 3 (OH) 3 . 



132. Phloroglucin occurs in the living cell only in solu- 

 tion in the cell-sap. It is best recognized by means of the 

 mixture of vanillin and hydrochloric acid proposed by Lindt 

 (I). This is prepared by dissolving .005 gram of vanillin in 

 .5 gram of alcohol and then adding .5 gram of water and 3 

 grams of concentrated hydrochloric acid. It is best to apply 

 this reagent to previously dried sections ; when, if phloro- 

 glucin be present, a light red color is produced, which later 

 becomes somewhat violet-red. Orcin gives a bright blue 

 color with a red shading ; and many other related substances 

 give no color. 



Very small quantities of phloroglucin are not recognizable, 

 on account of the red color of lignified membranes pro- 

 duced by the addition of hydrochloric acid (cf. 255 and 



257). 



According to Waage (I, 253), phloroglucin in the living 



cell takes up methylene blue as do the tannins. 



