Alnus 937 



or rounded at the base, short- or long-acuminate, with slight axil-tufts 

 beneath. 



*** Leaves with serrate lobules. 



11. Alnus glutinosa, Gaertner. Europe, Siberia, Western Asia, North Africa. 



See below. 

 Branchlets usually glabrous. Leaves obovate, cuneate at the base ; obtuse, 

 truncate or rounded at the apex ; with prominent axil-tufts beneath. 



12. Alnus glutinosa, Gaertner, var. barbata, Ledehour {Alnus barbala, C. A. Meyer). 



Caucasus. See p. 938. 

 Branchlets pubescent. Leaves elliptical, rounded at the base and apex, 

 covered on both surfaces with pubescence, densest on the midrib and 

 nerves beneath. 



13. Alnus tenuifolia, Nuttall. Western North America. Seep. 957. 



Branchlets glabrous. Leaves ovate, broad and rounded at the base, acute 

 or shortly acuminate at the apex, pubescent on the midrib beneath with 

 inconspicuous axil-tufts. 



14. Alnus subcordata, C. A. Meyer. Caucasus, North Persia. See p. 951. 



Branchlets pubescent. Leaves ovate-oblong, unequal and rounded or sub- 

 cordate at the base, cuspidate-acuminate at the apex, pubescent on the 

 midrib and nerves beneath. 



ALNUS GLUTINOSA, Common Alder 



Alnus glutinosa, Gaertner, De Fruct. ii. 54 (1791)5 Loudon, Arb. et Frut. Brit. iii. 1678 (1838); 



Willkomm, Forstliche Flora, 339 (1887); Mathieu, Flore] Fores tiire, 421 (1897); Winkler, 



Betulacece, 115 (1904). 

 Alnus nigra, Gilibert, Exerc. ii. 401 (1792). 

 Alnus communis, Desfontaines, Tabl. Hort. Paris, 213 (1804). 

 Alnus vulgaris, Persoon, Syn. ii. 550 (1807). 

 Betula Alnus glutinosa, Linnaeus, Sp. PI. 983 (1753). 

 Betula Alnus, Scopoli, Fl. Cam. ii. 233 (1772). 

 Betula glutinosa, Lamarck, Did. i. 454 (1783). 

 Betula palustris, Salisbury, Prod. 395 (1796). 



A tree, occasionally attaining 100 feet in height and 12 feet or more in girth. 

 Bark of young trees smooth and greenish ; after twenty years old becoming brownish- 

 black and divided on the surface into broad flattened plates. Young branchlets, 

 three-angled at the tip, usually glabrous, occasionally pubescent, covered with glands, 

 which secrete a waxy resin, often seen on the dried twigs as a bluish bloom. Leaves 

 (Plate 268, Fig. 6) averaging 3^ inches long and 3 inches broad, variable in shape, 

 but nearly always broadest above the middle, obovate, sub-orbicular or elliptical ; 

 cuneate at the base ; obtuse, truncate, or retuse at the apex ; margin entire in the 

 basal third, elsewhere lobulate, each lobule serrate or dentate ; upper surface dark 

 green, shining, glabrous ; lower surface light-green, pubescent along the midrib and 

 IV 2 G 



