Cascara sagrada (Rhamnus Purshiana, U.S.P.) is the dried bark of Rhamnus purshianus, DC. (N.O. Rhamneae), a shrub growing in North California, Oregon, and Washington. It is collected in the spring and early summer, and dried in the shade. It is generally considered that the action of the bark becomes milder and less emetic by keeping; hence matured bark (three years old) is preferred for pharmaceutical purposes. The transverse section exhibits a narrow purplish cork, a yellowish-grey cortex, in which groups of sclerenchymatous cells may be distinguished, and a brownish-yellow bast, containing wavy, medullary rays. The odour is characteristic, though not powerful; the taste is nauseous and persistently bitter.
