CRUDE DRUGS. 



543 



principle resembling pyrocatechin ; npon fusion with potassium 

 hydrate a phenol similar to protocatechuic acid is formed ; dilute 

 solutions are colored olive-brown with ferric chloride and possess 

 a slight fluorescence ; alkalies give a deep red color to the solutions. 



Fig. 238. Southern prickly ash [Fagara (Xanthoxylum) Clava-Herculis]: A, transverse 

 section showing cork (k), stone cells (st), groups of primary bast fibers (b), calcium oxalate 

 (ca), medullary rays (m), parenchyma (p) containing starch, oil-secretion reservoirs (o), 

 sieve (s), cambium (c); B, isolated stone cell showing pores and lamellae; C, group of bast 

 fibers found in young, thin bark and surrounding parenchyma (p); D, longitudinal section 

 near a group of bast fibers showing non-lignified bast fibers (b), calcium oxalate (ca) in 

 crystal fibers, medullary rays (m), parenchyma (p) containing starch. 



Allied Plants. Oucrciis robcr, indigenous to Europe, is 

 the source of the bark used in England and Continental Europe ; 

 the bark closely resembles that of Quercus alba, but the periderm 

 is not removed; it contains from 10 to 16 per cent, of tannin, 

 besides gallic and ellagic acids. Quercus velutina, or black oak, 

 yields the quercitron bark, which resembles that of Quercus alba 



