148 TREES OF THE NORTHERN UNITED STATES 
2. Alnus serrulata, Willd. (SmMooTH 
ALDER.) Leaves 2 to 41% in. long, thick- 
ish, obovate, acute at base, sharply and 
finely serrate, green both sides, smooth or 
often downy Seneath; stipules yellowish 
green, oval, and falling after 2 or 3 leaves 
have expanded above them. Fruit ovate. 
Rather 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 
tree 30 ft. high. 
A. serrulata. 
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, 4% to 
1 in. long, 14 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 glutinésa, L. (EUROPEAN 
ALDER.) Leaves roundish, wedge- 
shaped, wavy-serrated, usually abrupt 
at tip, glutinous; sharply and deeply 
incised in some varieties. Fruit oval, 
44 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), 
A. glutindsa. and rubrinervis (red-leaved). 
5. Alnus cordifdlia, 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. Oe cordifolia, 
