148 



TREES OF THE NORTHERN UNITED STATES 



2. Alnus serrulata, Willd. (SMOOTH 

 ALDER.) Leaves 2 to 4J^ in. long, thick- 

 ish, obovate, acute at base, sharply and 

 finely serrate, green both sides, smooth or 

 often downy beneath; stipules yellowish 

 green, oval, and falling after 2 or 3 leaves 

 have expanded above them. Fruit ovate. 

 Bather a shrub than a tree, 6 to 12 ft. high, 

 common along streams south of 41 N. Lat. 

 In the Southern 

 States it some- 

 times forms a 



A. serruiata. 



tree 30 ft. high. 



3. Alnus maritima, Muhl. (SEASIDE 



ALDER.) Smooth ; leaves oblong-ovate to 



obovate, with a tapering base, sharply ser- 

 rulate ; petiole slender; color bright green, 



somewhat rusty beneath. Flowering in 



the autumn. Fruiting catkin large, % to 



1 in. long, j in. thick, usually solitary, 



ovoid to oblong. A small tree, 15 to 25 ft. A. maritima. 



high. Southern Delaware and eastern 

 Maryland, near the coast. 



4. Alnus glutinosa, L. (EUROPEAN 

 ALDER.) Leaves roundish, wedge- 

 shaped, wavy-serrated, usually abrupt 

 at tip, glutinous; sharply and deeply 

 incised in some varieties. Fruit oval, 

 y z in. long. A medium-sized tree, 25 

 to 60 ft. high, of rapid growth, often 

 cultivated under several names; the 

 most important being vars. laciniata 

 (cut-leaved), quercifolia (oak-leaved), 

 and rubrinervis (red-leaved). 

 5. Alnus cordifolia, Ten. (HEART-LEAVED 



ALDER.) Leaves heart-shaped, dark green 



and shining. Flowers greenish-brown, bloom- 

 ing in March and April, before the leaves 



expand. A large and very handsome Alder, 



15 to 20 ft. high, growing in much dryer soil 



than the American species. Cultivated from 



southern Europe. Hardy after it gets a good 



start, but often winter-killed when young. 



A. erlutln6sa. 



