472 



EXOGENOUS OR DICOTYLEDONOUS PLANTS. 



edible seeds are too well known to need enumeration. The as- 

 tringent bark and leaves of the Oak abound in tannin, gallic acid, 

 and a bitter extractive called Quercine ; they are used in tanning 

 and dyeing. Quercitron is obtained from the Quercus tinctoria. 

 Galls are swellings on the leafstalks, &c., when wounded by cer- 

 tain insects ; those of commerce are derived from Q. infectoria 

 of Asia Minor. Cork is the exterior bark of the Spanish Quercus 

 Suber. 



1043 



1045 



1044 



879. Ord, MyricaceSD (the Sweet-Gale Family). Shrubs, with al- 

 ternate and simple aromatic leaves, dotted with resinous glands ; 

 monoecious or dioecious. Differs from the next principally by the 

 one-celled ovary, with a single erect orthotropous ovule, and a 

 drupe-like nut. Ex. Myrica, Comptonia, the Sweet Fern. The 

 drupes of M. cerifera (our Candleberry) yield a natural wax. 



880. Ord, Betlllaceae (the Birch Family). Trees or shrubs, with 

 alternate and simple straight-veined leaves, and deciduous stipules. 

 Flowers monoecious ; those of both kinds in aments and commonly 

 achlamydeous, placed three together in the axil of each three-lobed 



FIO. 1042. Quercus Chinquapin in fruit: a, cluster of sterile aments. 1043. A magnified 

 staminate flower. 1044. Transverse section of an ovary, showing the three cells with two 

 ovules in each. 1045. The immature seed, with the accompanying abortive ovule. 1046. The 

 nut (acorn), in its scaly involucre, or cupule. 1047. Vertical section of the same, and of the 

 included seed and embryo, showing the thick cotyledons. 



