CORTEX RHAMNI PURSHIAN.E. CASCARA. 1 57 



CORTEX RHAMNI PURSHIAN^. CASCARA. 



Rhamnus Purshiana (Cascara Sagrada) . — Chittem Bark. 

 The bark of Rhamnus Purshiana, De Candolle (nat. ord. 

 Rhamnaceco). Habitat, northwestern United States. 



Description. — Occurs in quills or curved pieces, about 

 3 to 10 cm. long, and about 2 mm. thick; outer surface 

 browTiish-gray and whitish; the young bark having 

 numerous, rather broad, pale-colored warts; inner sur- 

 face yellowish to light brownish, becoming dark brown 

 with age ; smooth or finely striate ; fracture short, yellow- 

 ish, in the inner layer of thick bark somewhat fibrous; 

 inodorous ; taste bitter. 



The medullary rays are thin and extend about three - 

 fourths of the wddth across the bark. They occur in 

 groups which converge at their outer ends, thus differing 

 from Rhamnus Calif ornica. Stone cells are present, thus 

 distinguishing it from Rhamnus frangula. Powdered 

 bark turns orange on the addition of alkalies. Rhamnus 

 Calif ornica turns a deep red. 



Powder. — The powder shows the following elements: 

 Crystals, starch, resin, cork, bast fibres, parenchyma, 

 medullary ray tissue, stone cells, and fragments of long- 

 celled tissues from the phloem part of the fibro-vascular 

 bundles. 



Crystals are the most characteristic constituents of the 

 powder. These are usually in great abundance and 

 are particularly prominent in a fine powder. The 

 rosette forms are the most common; these vary in 

 size, but on the average run about 15 to 20 microns. 

 Cubical crystals are found clinging about the bast fibres 

 in numbers; these are smaller, averaging between 5 and 

 10 microns in a number of specimens examined. 



The starch grains are not of much diagnostic im- 

 portance, being simple, quite small, and usually incon- 

 spicuous. They average in size about 4 microns. 



