MICROSCOPICAL EXAMINATION 



503 



The first example is illustrated by the barks taken from the same genus 

 Frangula, Fig. 275, and Cascara sagrada, Fig. 276. A comparison of 

 the fragments composing these two powders shows them to be very similar 

 in structure. Cascara presents one striking difference, as shown by the 

 sclerenchymatous cells, sc, Fig. 276, which occur quite commonly, but 

 occur rarely, if ever, in Frangula. In each of the specimens are bast 

 fibers, but in Frangula the fibers have thicker walls and contain more 

 numerous and well-defined pits than do the fibers of Cascara. Also the 



PIG. 276. Powdered Cascara Sagrada Bark (RhamnusPurshiana). (X 210.) col, Collenchyma 

 oflthe cortex, cr, Prismatic and rosette crystals, fl. Bast fibers. /, V , Bast in longitudinal and 

 transverse section, pc, p'c'. Cortical parenchyma in longitudinal and transverse section, ph, 

 Phelloderm. rm. Medullary rays, tangential section, r'm' ', The same, transverse section. r"m", 

 The same, radial section, s, s 1 , Cork; in surface view and section, sc, Sclerenchymatous cells, tc, 

 Rows of crystal cells. (From Greenish and Collin.) 



cork cells and the large parenchyma cells of the cortex show characteristics 

 which are of diagnostic value. In Frangula the cork cells contain a deep 

 red or purplish coloring substance, while those of Cascara have a reddish- 

 brown coloring substance. In the large parenchyma cells of Cascara is 

 found a substance yellowish in color which changes to orange upon the 

 addition of potassium-hydrate solution, while in Frangula the large paren- 

 chyma cells contain a coloring substance of a much brighter yellow, which 

 upon the addition of potassium-hydrate solution changes to a red or deep 

 purplish color 



