35° MICROCHEMISTRY OF PLANT PRODUCTS 



three drops of concentrated sulphuric acid, they dissolve with a 

 yellow color, while, with like treatment, .inulin sphaerites dissolve 

 with a violet color. 



Indican. — The glucoside indican is a substance of the con- 

 sistency of syrup, and of a yellowish or brownish color. It 

 is found in Isatis tinctoria, Phajus grandifolius, and in other 

 indigo-bearing plants. When tissues containing indican are 

 exposed to the air, they may take on a blue color due to the con- 

 version of the indican to indigotin, which may be precipitated 

 in alcohol in the form of small, tubular, bluish crystals. To 

 demonstrate the presence of indican, tissues containing it should 

 be placed under a bell-jar and over a dish of absolute alcohol. 

 After standing exposed to the vapor of alcohol for twenty-four 

 hours, the tissues will be colored blue by the indigo blue which 

 will have been formed from the indican. A piece of moistened 

 filter-paper should be placed under the bell-jar to keep the tissues 

 from drying. 



Inulin, CjjHjgOjj. — Inulin is a carbohydrate which occurs 

 dissolved in the cell-sap of many plants, particularly among 

 the Compositae. It may be deposited from its solution in the 

 cell-sap by means of alcohol. To study the sphserocrystals of 

 inulin, pieces of dandelion or Dahlia roots should be placed in 

 50 per cent, alcohol for a week or more, and then thin sections 

 should be prepared and examined in a drop of the alcohol under 

 the microscope. The sections should not be placed in water, 

 since the crystals of inulin are soluble in it. The sphserites will 

 appear applied to the walls of the cells as shown in Fig. 98. 

 When the alcohol is replaced by water which is then heated over 

 a flame, the sphserites will dissolve. If sections containing 

 inulin sphserites are treated with a 20 per cent, solution of «- 

 naphtol, and then 2 or 3 drops of concentrated sulphuric acid 

 are added, the sphserites will be seen to dissolve with a violet 

 color. Inulin does not reduce Fehling's solution. 



Leucin, CjHj^HNj.COOH. — Leucin belongs to the amido- 

 compounds. It has been found in the etiolated leaves of Pas- 

 palum elegans and Dahlia variabilis, and associated with as- 



