176 A TEXT-BOOK OF BOTANY. 



The drugs thus far studied may to some extent be grouped 

 according to the sublimable constituents which give characteristic 

 reactions. I. Thein- or caffeine-containing drugs, as coffee, tea, 

 cacao, and guarana. 2. Arbutin-containing drugs or those yielding 

 hydrochinon, as uva-ursi and other Ericaceae. 3. Drugs yielding 

 oxymethylanthraquinone and giving a distinct purple color with 

 solutions of the alkalies, as rhamnus purshianus, f rangula, rheum, 

 senna, etc. 



FIG. 103. Alkaloids of ipecac obtained by sublimation as follows: 0.050 Gm. of the 

 powdered drug is mixed with 2 drops of water on a glass slide and heated; the third dis- 

 tillate at a temperature of 100 to 115 C. gives colorless or yellowish, highly refractive 

 globules (A) in which crystals of emetin separate. B, Short, rod-shaped crystals of the double 

 alts formed on the addition of gold chloride to the globules of the oily distillate. C, Oily 

 globules of the distillate uniting and in which, upon the addition of potassium bismuth 

 iodide, small spherites arise. D, Crystals of the alkaloids formed on treating small sections 

 of ipecac or o.ooi Gm. of the powder with an aqueous solution of picric acid acidified with 

 hydrochloric acid. E, Crystals formed at edge of cover glass. After Tunmann in Gehe & 

 Co.'s Handelsbericht, 1912. 



Cell-sap Colors. The majority of the other color-substances 

 found in the higher plants besides the green and yellow principles 

 previously mentioned occur in solution in the cell-sap, and may 

 be in the nature of secondary substances derived from the plastid 

 pigments, or they may be produced directly by the protoplasm. 

 Upon making sections of the tissues containing cell-sap color- 

 substances, not infrequently strikingly contrasting colors are 

 observed in contiguous cells; as in the petals of the poppy and 



