$6 BOTANICAL MICROTECHNIQUE. 



inulin, in proportion to its abundance. But this author suc- 

 ceeded in obtaining from Dahlia roots large crystal-aggre- 

 gates of tyrosin by placing a transversely halved root in a 

 cylindrical vessel with the cut surface upward, and then fill- 

 ing the vessel with alcohol until about a third of the root 

 projected above the fluid. The tyrosin then usually crys- 

 tallized on the cut surface in a few days. 



b. Ellagic Acid, C 14 H a O a +2H f O. 



136. G. Gibelli (I) found in the stem and root of chestnut- 

 trees attacked by the " malattia dell' inchiostro" [ink-dis- 

 ease], sphaerocrystals of ellagic acid. These were soluble 

 in water and alkalies, and dissolved in potassium carbonate 

 Avith a yellow color, in concentrated nitric acid with a gar- 

 net-red color. Ferric chloride produced a greenish-black 

 color, and silver nitrate a red-brown one. 



3. Aldehydes. 

 Vanillin, C 6 H 3 .OH.OCH 3 .CHO. 



137. Vanillin occurs often on the surface of dried Vanilla 

 pods in the crystalline form ; but in their interior it is found 

 only dissolved or in the amorphous condition. It is readily 

 soluble in ether and alcohol, hardly soluble in cold water, 

 and more readily so in hot water. It is colored blue by 

 ferric chloride, but this reaction cannot be used microchem- 

 ically, according to Molisch (I, 47). Besides, vanillin gives 

 characteristic color-reactions with numerous organic com- 

 pounds. It gives a brick-red color with phloroglucin or 

 resorcin and sulphuric acid, a red-violet with phloroglucin 

 and hydrochloric acid, yellow with aniline sulphate, red with 

 orcin and hydrochloric acid, yellow with metadiamidobenzol, 

 carmine-red with thymol, hydrochloric acid and potassium 

 chlorate (cf. 254). 



Of these reagents the best adapted to microchemical use 

 are, according to Molisch, orcin and phloroglucin. The 

 first may be used conveniently in a 4% solution, the sections 

 to be tested being wet with it on the slide and then treated 



