252 BOTANY AND PHARMACOGNOSY. 



tain yellow coloring principles: Hicoria ovata, H. sulcata, and 

 H. glabra (pig-nut hickory) ; green coloring principles are found 

 in H. tomentosa, and yellowish-brown principles in Juglans nigra, 

 J. cinerea and /. regia. 



The fatty oils from the cotyledons (kernels) of both hickory- 

 nuts and walnuts are articles of commerce, and they have been 

 used in medicine. 



V. ORDER FAGALES. 



The plants are trees or shrubs with alternate, petiolate, simple, 

 pinnately veined leaves. The flowers are in aments, monoecious, 

 and with a more or less distinct perianth. The fruit is a nut which 

 is subtended by the mature involucre (bur or cup) or samara, 

 the seeds being without endosperm (Fig. 135). 



a. BETULACE^ OR BIRCH FAMILY.— The plants are 

 aromatic trees or shrubs and are represented in the United States 

 by such trees as hornbeam (Carpinus), ironwood (Ostrya), and 

 birch (Betula) ; and by such shrubs as the hazelnut (Corylus) and 

 alder (Alnus). The plants yield a volatile oil consisting largely 

 of methyl salic3'late. The bark of the sweet birch {Betula lenta) 

 yields the oil of betula which is official and closely resembles the 

 oil of wintergreen. The bark of a number of plants of this family 

 yields tannin and yellow coloring principles. A number of species 

 of Betula yield a sweet sap, as B. lenta, and B. Bhojpattra of Rus- 

 sia. The nuts of some species are edible, as the filbert or hazelnut 

 of Europe {Corylus Avellana), the hazelnut of the Orient (C. 

 Colurna), the American hazelnut (C. americana) . 



b. FAGACE.^ OR BEECH FAMILY.— This family in- 

 cludes some of our largest forest trees, these being rather charac- 

 teristic of temperate regions. They are all highly valued for their 

 timber and yield other valuable products besides. One notable 

 characteristic is that all of the chestnuts and oaks and some of the 

 beeches contain tannin in the wood, bark and leaves. The oaks 

 are further notable in being prone to the attack of gall-producing 

 insects, (various species of Cynips) whereby the peculiar excres- 

 cences known as galls are formed on the leaves and young shoots. 

 Among the oaks which yield galls rich in tannin are the follow- 



