524 



BOTANY AND PHARMACOGNOSY. 



southwestern part of British America (p. 326). The bark is col- 

 lected in spring and early summer, and kept at least one year 

 before being used. 



Description. — Usually in flattened or transversely curved 

 pieces, occasionally in quills 2 to 10 cm. long, i to 3 cm. in diam- 

 eter, bark i to 3 mm. thick ; outer surface dark brown or brownish- 

 red, frequently completely covered with grayish or whitish lichens 

 (Fig. 229), several of which are peculiar to this bark, and with 



Fig. 229a. Transverse section of inner bark of Rhamnus Purshiana: st, group of 

 stone cells; b, groups of bast fibers surrounded by crystal fibers; m, medullary rays; sb, 

 sieve cells; parenchyma containing rosette aggregates of calcium oxalate. — ^After Vogl. 



small groups of brownish apothecia, longitudinally writikled, 

 sometimes with numerous lenticels 3 to 6 mm. long ; inner surface 

 light yellow or reddish-brown, smooth, longitudinally striate, turn- 

 ing red when moistened with solutions of the alkalies ; fracture 

 short, with projections of bast fibers in the inner bark, the medul- 

 lary rays one to two cells wide, forming converging groups; in 

 cross section the inner surface of the bark indistinctly crenate'; 

 odor distinct; taste bitter, slightly acrid. 



