164 SCIENTIFIC AND APPLIED PHARMACOGNOSY 



valuable for tanning. The wood varies in color, is firm and tough in 

 texture and is used for highly ornamental furniture. The hazlenut 

 or filbert is chiefly known for its edible nuts, yet the tree serves many 

 other useful purposes. 



The wood of the plants of this family is extremely tough and 

 flexible and the branches are used in the making of fishing rods, 

 hurdles, crates and, when split, into hoops for casks. The wood like 

 that of the birch is used in the manufacture of charcoal. The forked 

 twigs of the European hazel were formerly used like those of witch- 

 hazel as a divining rod. 



The cork arises in the outermost layers of the bark, forming 

 large plates, so that it can be removed in large pieces. The exfoliating 

 cork of the birch is also distinguished by the long, linear, transverse 

 lenticels. The bark is free from secondary bast fibers and usually 

 contains numerous groups of stone cells. In Betula and Alnus the 

 tracheae possess bordered pores and scalariform thickenings. A 

 mucilaginous epidermis is not of infrequent occurrence in the leaves 

 and the stomata usually occur only on the lower surface. The hairs 

 are both non-glandular and glandular, and glandular scales occur 

 on species of Betula and Alnus. Calcium oxalate occurs in the form 

 of rosette aggregates and solitary crystals. 



BETULA LENTA. Cherry, or Sweet Birch. The bark of the 

 trunk and larger branches of Betula lenta, a handsome tree and the 

 most conspicuous of American birches, yields a volatile oil known as 

 oil of birch. It is obtained from the bark by first macerating the 

 pieces with water and then distilling the oil by means of copper stills. 

 The oil does not pre-exist in the bark, but is formed from a glucoside, 

 gaultherin. The latter forms colorless needles and is soluble in 

 alcohol and water. It is very easily decomposed, even being hydro- 

 lysed in alcohol of 94 per cent. The bark also contains about 3 per 

 cent of tannin. 



CORTEX BETULA. Birch Bark. The bark of the European 

 white birch (Betula verrucosa) is used to some extent in medicine. 

 The bark of the older branches and trunk is collected, and after 

 removing the periderm, is carefully dried. 



It consists of more or less flattened pieces from 0.5 to 2 cm. 

 in thickness. The outer surface is orange-yellow, with whitish 

 patches and occasional scales of cork; inner surface yellowish-brown, 

 smooth and finely wrinkled; fracture granular and even; odor slight 

 and taste bitter. 



The bark is distinguished by not having any bast fibers, these 

 being replaced by stone cells which occur in groups forming an inter- 



