The Natural System of Botany. 333 



vated. The foliage is silvery, and covered with a kind of 

 scurf. 



Ulmace m. The Elm Tribe. A small order, of which Ul- 

 mus (The Elm) is the principal genus. The mucilaginous bark 

 of the Slippery Elm is the only medicinal product. 



Saururace^e. Aquatic herbs. Ex.: Saururus (Lizard's- 

 tail). No important properties. 



Ceratophyllacejb. Consists of the single genus, Cerato- 

 phyllum, a floating plant sometimes called Horn wort. 



CallitrichacejE. Also contains a single genus, common 

 to both Europe and America, Callitriche, a little aquatic herb. 



Podostemace^e. Insignificant aquatics. Ex. : Podoste- 

 mum (Thread-foot.) 



Euphorbiacejs. The Spurge Tribe. A small order, but 

 containing some important plants. Their properties are gene- 

 rally acrid and poisonous, contained in their milky juice. The 

 root-stock of one species furnishes Tapioca ; the seeds of ano- 

 ther afford Castor-oil, and those of another Croton-oii. Box- 

 wood, the dye called Turnsole, and Caoutchouc are the pro- 

 ducts of other species. Some of the order are violently poison- 

 ous, and their juice will immediately blister the skin. 



EmpetracejE. The Crow-berry Tribe. Small evergreen 

 shrubs. Ex. : Empetrum (The Crow-berry). 



JuglandacEjE. The Walnut Tribe. In this order are 

 found some of the most valuable timber trees, as Black Wal- 

 nut, and Hickory. Some of them also afford edible nuts. 



Cupulifer^e. The Oak Tribe. Important trees. Ex.: 

 Quercus (The Oak), Castanea (The Chestnut), Corylus (The 

 Hazel), Carpinus (The Hornbeam). The bark is mostly astrin- 

 gent. 



MTRicACEiE. The Gale Tribe. Aromatic shrubs. Ex.: 

 Myrica (Sweet Gale, Bayberry, Candle-berry or Wax Myrtle), 

 Comptonia (Sweet Fern). 



Betulace J3. The Birch Tribe. Trees and shrubs. Ex. : 

 Betula (The Birch), Alnus (The Alder). 



Salicaceje. The Willow Tribe. Ex. : Salix (The Wil- 

 low), Populus (The Poplar). The bark is astringent and 

 tonic. 



Balsamifluje. Contains the single genus Liquidambar, 



