522 



BOTANY AND PHARMACOGNOSY. 



light brown or brownish-black apothecia ; inner surface yellowish 

 or dark brown, smooth, longitudinally striate, and reddened by 

 alkalies; fracture short, with projecting bast fibers in inner bark; 

 odor slight ; taste slightly bitter. 



Inner Structure. See Fig. 228. 



Constituents. A glucoside frangulin (rhamnoxanthin), 

 which forms yellow crystals, is insoluble in water and nearly so in 

 alcohol, gives a bright purple color on the addition of solutions 



h 



^ 



... 



m m 



Fig. 228. Transverse section of inner bark of Rhainmts Frangida: b, bast fibers; 

 surrounded by crystal fibers; m, medullary rays; parenchyma containing rosette aggre- 

 gates of calcium oxalate. After Vogl. 



of the alkalies, and on hydrolysis yields rhamnose and emodin 

 fsee Rhubarb). It also contains the glucoside pseudofrangulin 

 (frangulic acid), which yields pseudoemodin ; rhamnoxanthin, a 

 coloring principle ; a volatile oil ; tannin ; starch ; calcium oxalate ; 

 and ash 5 to 6 per cent. 



Allied Plants. The bark of Rhauinus CarnioJica has been 

 substituted for R. Fraiv^ula. The older pieces are distinguished 

 by having a deeply fissured cork and groups of stone cells. In 



