512 A TEXT-BOOK OF BOTANY. ^ 



or Aleppo galls (pp. 206, 334) ; Quercus Rohur, which is some- 

 times divided into Q. piibescens and Q. pedunculata, yields 

 a European gall; the live oak (Q. virginiana) of Texas; and 

 Q. lobata of California. Various oaks of the Southern States also 

 produce ''ink balls " or " ink galls," as Q. coccinea and Q. imhri- 

 caria. Several species of oak are used in the tanning industry, 

 as that of white oak {Quercus alba), red oak (Q. rubra), Spanish 

 oak (Q. digitata), and black oak (Q. vclutuia), all of North 

 America ; Q. pedunculata and sessiliflora of Germany, and Q. den- 

 tata of Japan. , 



The glucosidal coloring principle quercitrin is found in the 

 bark of Quercitron or black oak (Q. velutina) . Q. coccifera of 

 Southern Europe yields a red coloring principle which is used in 

 dyeing. 



The wood of the American beech (Fagi^s americana) and of 

 the European red beech (F. sylvatica) yields a tar from which 

 on distillation the official creosote is obtained. 



The cork of commerce which is used for a variety of purposes 

 is derived from the bark of several species of Quercus, namely, 

 Q. Suber and Q. occidentalis, growing in Spain, Southern France, 

 and Algiers. 



The cotyledons of the seeds of the Beech family are rich in 

 proteins, starch, and oil, and some of the nuts are edible, as the 

 Spanish chestnuts obtained from Castanea vulgaris^ American 

 chestnut from C. dentata, and chinquapin from C. puuiila (Fig. 

 202). 



VI. ORDER URTICALES. 



This order embraces three families which, while they agree in 

 certain characters, are quite distinct in other ways. 



a. ULMACE^ OR ELM FAMILY.— The plants are trees 

 or shrubs with alternate, simple, serrate, petiolate leaves. The 

 flowers are monoecious or dioecious, with a 4- to 6-divided peri- 

 anth. The fruit is a i -seeded drupe, samara, or nut. The typical 

 group of this family is that of the elms, of which the American 

 or white elm (Ulmiis americana) is the most prized for orna- 

 mental purposes. The elms yield valuable timber, and the bark of 

 Ultnus campestris of Europe is used for tanning and dyeing be- 

 cause of the presence of tannin and a yellow coloring principle. 



