Betula michauxii
Betula neoalaskana
bouleau de Michaux, Michaux's birch, Newfoundland dwarf birch
Alaska birch, Alaska paper birch, northwestern white birch, paper birch, resin birch
of young trunks and branches reddish brown, when mature becoming pinkish white to light red (starkly white in interior Alaska;
D.
without taste and odor of wintergreen, moderately to densely pubescent, not conspicuously resin-coated, without large, warty, resinous glands.
glabrous, covered with conspicuous resinous glands.
blade obovate–reniform, with 2–3 pairs of lateral veins, 0.5–1 × 0.5–1.2 cm, base cuneate, margins deeply crenate-dentate, apex broadly rounded to nearly truncate;
surfaces abaxially usually glabrous.
blade deltate-ovate with 5–18 pairs of lateral veins, 3–8 × 2–6 cm, base rounded or broadly cuneate, margins coarsely doubly serrate, apex long-acuminate;
surfaces abaxially glabrous to sparsely pubescent, pubescent along major veins and in vein axils, covered with small resinous glands.
erect, short-cylindric, 0.5–1 × 0.5–0.8 cm, shattering with fruits in fall;
scales unlobed (lateral lobes sometimes present but greatly reduced), glabrous.
pendulous, cylindric, 2–4 × 0.8–1.2 cm, shattering with fruits in fall;
scales glabrous, margins ciliate, lobes diverging distal to middle, central lobe narrower and equal to or slightly shorter than lateral lobes, lateral lobes broadly angular, extended.
with wings not apparent or reduced to narrow ridges.
with wings broader than body, broadest near summit, extended beyond body apically.
.
, pers.
.), smooth, exfoliating in thin sheets.
= 28.
Betula michauxii
Betula neoalaskana
This infrequent dwarf birch is distinguished from Betula nana mostly on the basis of its reduced infructescence scales and wetter habitat (J. J. Furlow 1984), characteristics that are also occasionally noted in B. nana. It perhaps might better be treated as a race of that species; in the absence of thorough study of this complex, however, it seems best to follow the traditional treatment (M. L. Fernald 1950c; J. Rousseau and M. Raymond 1950).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Betula neoalaskana belongs to a circumpolar complex including B. pendula Roth and B. populifolia Marshall (but not B. papyrifera Marshall, with which it has sometimes erroneously been merged). It is most closely related to the Asian members of this group, including B. japonica Siebold, B. mandshurica (Regel) Nakai, and B. platyphylla Sukaczev (T. C. Brayshaw 1976). The species was formerly widely known by the name B. resinifera (Regel) Britton, but that name has been shown to be illegitimate (B. Boivin 1967–1979, 15: 414–418; J. R. Dugle 1969). The name was based on a mixture of Siberian and North American material and has never been lectotypified.
Betula neoalaskana Sargent is known to hybridize with B. papyrifera Marshall, producing B. ×winteri Dugle, and with B. glandulosa, producing B. ×uliginosa Dugle.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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