416 SCIENTIFIC AND APPLIED PHARMACOGNOSY 



of this family contain either idioblasts having brown contents, 

 secretory cavities containing a brown amorphous substance, or mucil- 

 age cavities. The latter when present are of lysigenous origin, and 

 are distributed in the parenchyma of the cortex and in the veins of 

 the leaves. The walls of the epidermal cells sometimes are modified 

 to mucilage. The leaf-teeth are differentiated into glands and the 

 non-glandular hairs are either unicellular, uniseriate or stellate. 

 Glandular hairs do not occur. The tracheae are marked by simple 

 pores except when in contact with the medullary rays, the dividing 

 wall possesses bordered pores. The wood fibers are marked by 

 simple perforations. 



RHAMNUS PURSHIANUS. Cascara Sagrada. The bark of Rham- 

 nus Purshianus (Fam. Rhamnacese), a shrub indigenous to northern 

 California, Washington, Oregon and the southwestern part of British 

 America. The bark is collected 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. in length, 1 to 3 cm. in breadth, 

 bark 1 to 3 mm. in thickness; outer surface dark brown or brownish- 

 red, frequently completely covered with grayish or silvery whitish 

 lichens, several of which are peculiar to this bark, and with small 

 groups of brownish apothecia, longitudinally wrinkled, sometimes 

 with numerous lenticels 3 to 6 mm. in width and occasionally with 

 adhering mosses, inner surface light yellow of reddish-brown, smooth, 

 longitudinally striate, turning red when moistened with solutions of 

 the alkalies; fracture short, with projections of bast fibers in the inner 

 bark, the medullary rays 1 to 2 cells in width, forming converging 

 groups; in cross-section the cambium margin is indistinctly crenate; 

 odor slight, distinct; taste bitter, slightly acrid and disagreeable. 



Inner Structure. (Figs. 177 and 178.) Periderm of usually a 

 number of layers of rectangular thin-walled, yellowish-brown or 

 reddish-brown cork cells, a number of which have a brown amor- 

 phous content; a hypodermis of several layers of collenchymatous 

 cells having a dark-brown color; primary cortex of tangentially- 

 elongated cells and numerous large groups of stone cells having very 

 thick, strongly lignified, finely lamellated walls, and in which the 

 lumina are very small; medullary rays 1 to 4 cells in width, 15 to 25 

 cells in height, the contents being frequently colored red upon the 

 addition of solutions of the alkalies; bast fibers in tangentially elon- 

 gated groups in the inner bark, the walls being thick and strongly 

 lignified; crystal fibers around the bast fibers with individual crys- 

 tals from 0.008 to 0.015 mm. in length; parenchyma with spher- 



