CLASSIFICATION OF ANGIOSPERMS. 509 



nigra yields a volatile oil, of which the important constituent is 

 humulene. 



The charcoal used medicinally is prepared by burning the wood 

 of the young shoots of the white and black willow, poplar, beech, 

 or linden without access of air. 



III. ORDER MYRICALES. 



This group somewhat resembles the Salicales in that the flowers 

 are in aments. The flowers are either pistillate or staminate, 

 and mostly dioecious in our native species. The most important 

 family is the MYRICACE^E or Bayberry Family. The genus Myrica 

 is especially characterized by the fact that the outer layer of the 

 drupe is waxy. This is particularly true of the following species : 

 Myrica cerifera, the wax myrtle of the sandy swamps of the United 

 States, contains a volatile oil. The fruit of sweet gale (M. Gale) 

 yields a volatile oil containing a camphor. The sweet fern ( Comp^ 

 tonia peregrina) found in the United States yields a volatile oil 

 resembling that of cinnamon. The rhizome of this plant contains 

 also tannin and possibly gallic and benzoic acids. 



IV. ORDER JUGLANDALES. 



The plants are trees with alternate, pinnately-compound leaves. 

 The staminate flowers are in drooping aments, the pistillate being 

 solitary or several together. The flowers are monoecious and 

 have a more or less distinct perianth consisting of 3 to 6 lobes. 

 The fruit is a kind of drupe formed by the union of the torus 

 with the wall of the ovary. There is but one family in this order, 

 namely, the JUGLANDACE^E (Walnut family), which includes the 

 hickory (Hicoria) and walnut. The black walnut (Juglans 

 nigra) of the United States yields a valuable timber and an edible 

 nut; the white walnut or butternut (/. cinerea) of the United 

 States yields the butternuts which are edible, and a bark which has 

 medicinal properties and was formerly official under the name of 

 JUGLANS. It contains about 7 per cent, of a yellow, crystalline 

 acrid principle which is colored purple with alkalies ; 2 to 2.5 per 

 cent, of a crystalline resin; volatile oil, tannin, sugar, and a 

 fixed oil. The bark of the stems of the butternut tree is used in 

 dyeing. The ripe fruits are edible, as also* the green nuts when 



