220 POPULAR ECONOMIC BOTANY. 



however is giving way to the mineral colours, in conse- 

 quence of its want of permanency — the fault of most 

 vegetable colours. The consumption is still very con- 

 siderable, amounting to between 500 and 600 tons per 

 annum. 



Shumac or Sumach.— The dried and powdered leaves of 

 Rhus Cotinus. (Nat. Ovd. Anacardiacea.) (Plate XV. fig. 79.) 



This material was known to the ancients, by whom it 

 was used for tanning as well as dyeing. It contains large 

 quantities of tannin, as well as a yellow colouring matter 

 similar to that yielded by fustic ; the wood of this plant 

 has been already described as young fustic. It is brought 

 to this country in small bags, of about one hundredweight 

 and a half. More than 13,000 tons were imported in 

 1852. 



OpvChella-weed. — Under this name are imported several 

 species of Roccella. (Nat. Ord. Lichenes.) 



The lichens which constitute the Orchella- weeds of com- 

 merce are of an ash-grey colour, and consist of long thin 

 flat thalli, or leaves, having a mealy appearance ; they are 

 about an inch and a half to two inches in length, and much 

 branched. 



The ancients were acquainted with one or more of the 



