42 LEAVES 



brown points when examined with a lens. The leaves have no marked 

 odour, but are strongly astringent and somewhat bitter. 

 The student should observe 



(a) The spathulate outline, entire margin, and rounded apex, 



(b) The veinlets depressed on 



the upper surface, 



(c) The absence of brown 



points on the under 

 surface ; 



and should compare the leaves with 

 (i) Buchu leaves, which have 



a toothed margin, 

 (ii) The substitutes mentioned 

 below. 



Constituents. Bearberry leaves 

 contain both tannin and gallic acid ; 

 an infusion of the leaves accordingly 

 gives a bluish black precipitate with 

 ferric salts. They also contain 

 arbutin, methyl - arbutin, ursone, 

 quercetin, and possibly myricetin. 



FIG. 28. -Bearberry. Reduced to Arbutin, .C 12 H 16 O 7 ,iH 2 0, crystallises 



about one-fourth natural size. in lon g white bitter needles melting at 

 (Maisch.) 168 and easily soluble in boiling water 



and in alcohol ; when hydrolysed with 



dilute sulphuric acid (or with emulsin) it yields dextrose and hydroquinone. 

 A similar decomposition takes place when arbutin is administered by the mouth, 

 both arbutin and hydroquinone being excreted by the urine ; in fact, the activity 

 of bearberry leaves is said to be partly due to the stimulant and antiseptic 



FIG. 29. Bearberry leaves. Natural size. 



properties of the latter substance. Arbutin has also been detected in several 

 other Ericaceous plants. 



Ursone, C 30 H 48 3 ,2H 2 O, has been obtained in tasteless, colourless, odour- 

 less crystals. 



Quercetin, C 15 H 10 7 ,2H 2 0, is a yellow crystalline body which occurs in the 

 fruits of Rhamnus infectoria, Linne, &c., and is also obtained when quercitrin, 



