MISCELLANEOUS DICOTYLEDONOUS PLANTS 97 



selections and substitutions of plants, the contents of this chapter are of world-wide 

 applicability. 



2. The members of the class in botany should make the test for coniin as follows: 

 Concentrated sulphuric acid colors coniin blood-red, the color gradually changing to 

 green. Potassium-cadmium iodide causes an amorphous precipitate of coniin, which dis- 

 tinguishes the latter from nicotin, yielding a crystalline precipitate. 



3. Study of sublimable principles. See for details KRAEMER, HENRY: Applied and 

 Economic Botany, 1914: 173-176 Quite a number of plant principles are capable of 

 being sublimed. Not only is this true, when they are in the pure state, but also when 

 they are associated with other compounds in the plant cell. This fact is of interest in 

 the examination of poisonous plants. The procedure is simple, and a small quantity 

 of material (0.020 to 0.050 gram) is required. In the study of flowers, a small piece 10 

 square millimeters is all that is required. The material is dried, and hence, the use- 

 fulness of the dried plants for laboratory study. The dried material is cut up, or 

 comminuted and placed in a small watch crystal, which is covered with a slide, or 

 another watch crystal, for the deposition of the sublimate. The watch crystal con- 

 taining the material is carefully heated on a sand bath, or on a bath containing sul- 

 phuric acid. The method is peculiarly suited for the study of the principles in the 

 ericaceous plants. Tunman (Berichte der Deutsche Pharmaceutische Gesellschaft, 

 1911, 312) examined some of the Ericaceae by the microsublimation method and found 

 that they contained arbutin. The latter is a widely distributed glucoside in the 

 family and yields upon treatment with solutions of emulsin, or hydrochloric acid, 

 the sublimable principle hydrochinon. The latter forms prisms and plates and may 

 be examined further with acetone solution, dilute solutions of ferric chloride and water. 

 Arbutin occurs in the leaves of Arctostaphylos Uva-ursi, Vaccinium myrtillus, Kalmia 

 angustifolia (see ante), Pyrola rotundifolia and species of Rhododendron. This method 

 can be used for the study of the sublimable principles in stramonium, podophyllin. 



