PLANTS. 331 



of Europe (P. tremula), and the western Cotton Tree 

 (P. angulata) (P. tremuloides) . 



The White Poplar American aspen. Leaves dark 

 green on petioles, two or three inches long, and laterally 

 compressed, so that they can scarcely remain at rest in 

 any position, and are thrown into excessive agitation by 

 the slightest breeze. \i. 



SIXTY-FIRST FAMILY. BETULACE.E. BIRCHWORTS. 

 The first of this race is 



The White Birch (Betula alba). Leaves triangular, 

 deltoid, very taper-pointed and serrate ; distinguished by 

 their beautiful green color. A beautiful tree, with 

 chalky-white bark, easily separable into sheets or layers. 

 If the trunk is bored into in the spring-time, a very sweet 

 sap is obtained. Grows in America from Pennsylvania 

 to Maine, but not so abundantly as in Northern Europe 

 or Asia, where it forms great forests. Flowers unsight- 

 ly ; both sterile and fertile arranged in drooping catkins ; 

 the wood valuable for fuel. ^ . 



The Erie or Alder (Alnus glutinosa). Leaves sub- 

 plicate, ovate, glutinous ; bark brownish-gray ; stem or 

 trunk about fifty feet high ; grows in swampy grounds 

 where no other tree will thrive. Flowers, male and 

 female, in pendulous catkins. Bark, very hard, is good 

 for firewood. The wood, often handsomely veined, is 

 excellent for wagon-making, mill-posts, and woodwork 

 of dams ; as, being harder even than that of the locust, 

 it does not decay in the water. Not good for burning, 

 and makes very poor charcoal. Bark of branches used 

 by tanners and dyers, h. 



The Plane Tree Butlomvood Sycamore (Plata- 

 nus occidentalis), a native of North America, but often 

 planted, as an ornamental tree, in Europe. The largest, 



