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 



I i 



7n tn 



Fig. 22S. Transverse section of inner bark of Rhamnus Frangula: h, 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 

 (see 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 Rhamnus CarnioHca has been 

 substituted for R. Frangula. The older pieces are distinguished 

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



