BIRCH FAMILY. 5il 
8. Betula nana l,. Dwarf Birch. (Fig. 1218.) 
Betula nana I,. Sp. Pl. 983. 1753. 
B. Michauxiti Spach, Ann. Sci. Nat. (II.) 15:195. 1841. 
A low diffuse shrub, similar to the preceding 
species, but the twigs glandless, puberulent or 
glabrous. Leaves orbicular, obovate, or reniform 
and wider than long, bright green, firm, glabrous, 
on both sides when mature, deeply and incisely 
crenulate, rounded at the apex, rounded, obtuse 
or cuneate at the base, 3/’-10’’ long; petioles 
rarely more than 1’’ long; staminate aments %4/— 
1’ long, solitary or clustered; pistillate aments ob- 
long, sessile or short-peduncled, erect or some- 
what spreading, 3’’-5’’ long; fruiting bracts gla- 
brous, the lower usually 3-lobed, the upper ovate 
or lanceolate, mostly entire; nut oblong, wingless 
or narrowly winged. 
Greenland and Labrador to Hudson Bay. Also in 
northern Europe and Asia. May-June. 
g. Betula pumila L. Low Birch. (Fig. 1219.) 
Betula pumila V,. Mant. 124. 1767. 
A bog shrub, 2°-15° tall, the twigs brown, be- 
coming glabrous, the young foliage densely 
brownish-tomentose. Leaves obovate, broadly 
oval or orbicular, rounded at both ends or some 
of them cuneate-narrowed at the base, rather 
coarsely dentate, when mature glabrous and 
dull green above, pale, persistently tomentose 
or becoming glabrous beneath and prominently 
reticulate-veined, %4/-114’ long; petioles 14%4//— 
3/ long; fruiting pistillate aments oblong-cylin- 
dric, erect, peduncled, 1’ long or less, about 3/7 
in diameter; bracts puberulent or ciliolate, the 
lateral lobes spreading at right angles, shorter 
than the middle one; nut oblong, mostly rather 
broader than its wings. 
In bogs, Newfoundland to western Ontario and 
the Northwest Territory, south to New Jersey, Ohio 
and Minnesota. May-June. 
Ge ALNUS Gaertn. Fr. & Sem, 2: Si, jl, Gl — Wafs)ti. 
Shrubs or trees, with dentate or serrulate leaves, few-scaled buds, and flowers of both 
kinds in aments, expanding before, with or after the leaves, making their first appearance 
during the preceding season, the staminate pendulous, the pistillate erect, clustered. Stam- 
inate flowers 3 or sometimes 6 in the axil of each bract, consisting of a mostly 4-parted peri- 
anth, 4 stamens and subtended by 1 or 2 bractlets; filaments short, simple; anther-sacs ad- 
nate. Pistillate flowers 2-3 in the axil of each bract, without a perianth, but subtended by 
2-4 minute bractlets; ovary sessile, 2-celled; styles 2; bracts woody, persistent, 5-toothed or 
erose. Nut small, compressed, wingless or winged. [Ancient Latin name derived from the 
Celtic, in allusion to the growth of these trees along streams. ] 
About 14 species, natives of the northern hemisphere and the Andes of South America, Besides 
the following, some 4 others occur in the western parts of North America. 
Nut bordered by a membranous wing on each side. 1. A. Alnobetula. 
Nut acute-margined, wingless. 
Leaves obovate, broadly oval or suborbicular, dull; aments expanding long before the leaves. 
Leaves finely tomentose or glaucous beneath. 2. A. tncana. 
Leaves green, glabrous or sparingly pubescent beneath. 
Leaves finely serrulate; foliage not glutinous; native. 3. A. rugosa, 
Leaves dentate-serrate; twigs glutinous; introduced tree. 4. A. glulinosa. 
Leaves oblong, bright green and shining above; amentsexpandinginautumn. 5. A. maritima. 
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