368 



SUBTERRANEAN ORGANS 



&c.). The rhizomes are dried and sold separately from the roots. 

 Those of R. offi,cinale resemble the Chinese drug, but, being more spongy, 

 shrink and wrinkle as they dry, and are softer to cut ; the white reticula- 

 tions are commonly absent, the white and red lines being parallel to 

 one another ; the star-spots are also fewer and more scattered. The 



FIG. 195. English Rhubarb (E. rhaponticum). A, trans- 

 verse section of rhizome ; B, transverse section 

 of root. Natural size. 



roots are readily distinguished by their long cylindrical shape and 

 distinctly and entirely radiate transverse section. The constituents 

 of this variety of English rhubarb are similar to those of the Chinese. 



The rhizomes of R. rhaponticum are also much shrunken and usually 

 pinkish in colour ; they may be readily distinguished by the transverse 

 section which exhibits a diffuse circle of isolated star-spots. Rhapontic 

 rhubarb contains no emodin, aloe-emodin, or rhein ; its most charac- 

 teristic constituent is a crystalline glucoside, rhaponticin (rhapontin, 





