286 



THYAIELACEJE. 



fCHAP. 



Several Oaks abound in astringent principles, and the 

 bark of the English Oak, and acorn-cups of the Valonia 

 {Q. /Egilops and allied species), are largely used in Britain 

 by tanners. Gallic acid — used in making ink, from the 

 intense black colour of its combination with salts of iron — 

 and tannin are chiefly obtained from galls produced upon 

 scrubby Oaks of Asia Minor by the puncture of insects. 

 The gall is a diseased development of tissue induced by 

 the puncture. Cork is the outer bark of a South European 

 and Mediterranean Oak. It is collected at intervals of six 

 to ten years, after the tree has attained an age of about 

 thirty years. The bark is heated, flattened under weights, 

 and then slowly dried. The process of barking is said not 

 to injure the tree. 



87. Natural Order, T/iyine/accce. — The Spurge-Laurel 

 Family. 



Shrubs with stringy bark. Ovary free, one-celled (or two- 

 celled), with one pendulous ovule in each cell. 



Type — Paper Daphne [Daphne papy raced). 



A shrub (native of the Himalaya) with alternate, entire, 

 smooth leaves, and terminal heads of regular white flowers. 



