462 POWDERED VEGETABLE DRUGS 



165. (Fig. 161.) RHEUM. Rhubarb. U. S. 

 Fl. ex. 30. Fine powder. 



Rhabarber, G. Rhubarbe, Fr. 



The peeled older roots of Rheum officinale Bail., R. palmatum L. 

 and of other species and varieties of Rheum, Polygonacese. 



Brownish yellow. 



Aromatic; not pleasant. 



Very astringent and bitter. 



Parenchyma cells rather large and thin-walled, loosely united, 

 with compound starch granules (mostly twos and threes) and yellowish 

 brown resin; besides very numerous large aggregate crystals of calcium 

 oxalate. Reticulate ducts. 



Ash 9 per cent. 



Adulterated with roots of related species and varieties which re- 

 semble the official very closely histologically. R. rhaponticum (Euro- 

 pean rhubarb) and several other kinds are richer in starch, but other- 

 wise similar. Also adulterated with curcuma, flour, starches, etc. 



