274 INTRODUCTION TO PLANT GEOGRAPHY [CHAP. 



in the wild state and include the woods of Quebracho and Sweet 

 Chestnut, the leaves of Sumac and Gambier, such fruit products as 

 myrobalan, tara, and valonia (from the Turkish Oak), root materials 

 from Tanner's Dock and Palmetto, and barks of Hemlock, various 

 Oaks, Mangroves, Eucalypts, Wattles (Acacias), Larches, Spruces, 

 Birches, and Willows. However, the tannin content in the last four 

 instances is too low to warrant their general use. Tannin-inks are 

 the most important inks at the present time, their tannin being 

 derived largely from the insect galls formed in great abundance on 

 the twigs of the Aleppo Oak ; to these galls or an extract made from 

 them are added an iron salt, an agglutinant such as gum arable, and 

 a colouring matter such as logwood {see below). Other inks, too, 

 are made substantially from plant products. 



Of natural dves and stains obtainable from plants there is a vast 

 arrav involving almost all colours, though latterly most have been 

 supplanted at least in part by the synthetic or aniline dyes obtained 

 from coal-tar products. Such ' artificial ' dyes tend to be brighter, 

 cheaper, and more lasting, and with them only a few vegetable dyes 

 compete nowadays. These vegetable dyes are especially useful in 

 dyeing fabrics, but are also employed to colour a wide range of 

 other familiar products. Some of the more important of these 

 natural colouring matters, grouped according to the plant part from 

 which they come, are : from seeds and fruits — annatto, Persian berries, 

 and sap green ; from flowers — safflower and saffron ; from barks 

 — quercitron, lokao, and gamboge (an exuded gum resin) ; from 

 leaves — indigo, henna, woad, and chlorophyll (which is harmless 

 and consequently used in foods and toothpastes) ; from woods — 

 logwood or haematoxylin (of which many thousands of tons are 

 used annually to give colours ranging from reds to purples and 

 black), fustic, cutch, osage orange, sappanwood, and brazilwood ; 

 and from roots and tubers — alkanna, madder, and turmeric. Lichens 

 yield some fine dves, among which archil and litmus still find 

 extensive use. 



Essential Oils and Scents (Perfumes) 



Very different from the fatty oils already considered are the 

 so-called essential oils which have a pleasant taste and strong aromatic 

 odour, easily volatilizing in air. They are complex in chemical 

 nature but tend to be readily removed — by distillation, expression, 

 or solvent-action — from the many and various plants that produce 



