Salix humboldtiana
Salix fuscescens
Humboldt's willow
Alaska bog willow
decumbent or trailing;
branches yellow-brown, glabrous;
branchlets red-brown, gray-brown, or yellow-brown, glabrous.
stipules absent or rudimentary;
petiole 2–5.6(–6.4) mm;
largest medial blade hypostomatous, narrowly oblong, oblong, obovate, or broadly obovate, (14–)17–27(–45) × 7–21 mm, 1.4–2.5 times as long as wide, base cuneate or convex, margins slightly revolute or flat, entire, or serrulate to crenate proximally, (glands marginal), apex convex, acuminate, or rounded, abaxial surface glaucous, glabrous, adaxial slightly or highly glossy, glabrous;
proximal blade margins entire, (sometimes hairs ferruginous abaxially);
juvenile blade glabrous.
abaxial nectary absent, adaxial nectary oblong, 0.5–0.8 mm;
filaments distinct or connate less than 1/2 their lengths, glabrous;
anthers ellipsoid or shortly cylindrical, 0.3–0.4 mm.
abaxial nectary absent, adaxial nectary oblong, 0.4–0.9 mm, shorter than stipe;
stipe 0.8–2.5 mm;
ovary obclavate, pubescent or short-silky to glabrescent, hairs (often ferruginous), flattened or ribbonlike, beak abruptly tapering to styles;
ovules 8–12 per ovary;
styles connate or distinct distally, 0.1–0.4(–0.65) mm;
stigmas slenderly or broadly cylindrical, 0.24–0.3–0.68 mm.
5.5–8 mm.
humboldtiana Willdenow: Humboldt willow is not known to occur in the flora area.
is characterized by: trees, 4–25 m;
branches highly brittle at base, bud-scale margins distinct and overlapping adaxially;
stipules on late leaves rudimentary or foliaceous;
largest medial leaf blade usually linear, abaxial surface not glaucous, adaxial dull; pistillate bract deciduous after flowering;
stamens 3–7;
capsules with distinct, often raised, white veins.;
it occurs throughout much of Mexico to central Chile.
staminate 8–58 × 5–19 mm, flowering branchlet 0.5–15 mm; pistillate moderately densely to loosely flowered, slender, stout, or subglobose, 13.5–64(–70 in fruit) × 6.5–15 mm, flowering branchlet 4–18 mm;
floral bract brown or bicolor, 0.8–1.6 mm, apex rounded, entire, abaxially sparsely hairy, hairs (usually white, sometimes also ferruginous), wavy or straight.
= 38.
Salix humboldtiana
Salix fuscescens
Salix humboldtiana is closely related to S. nigra in its generally narrow leaf blades, which are not glaucous abaxially. The two differ in the following characters: S. humboldtiana has leaf blades linear to sometimes narrowly oblong (10–28.6 times as long as wide), ovaries usually ovoid to ellipsoid, ovary walls often stomatiferous and with raised, white veins, and capsule valves relatively thick, slightly recurved. S. nigra has leaf blades usually narrowly lanceolate (6–13 times as long as wide), ovaries pyriform to obclavate, ovary walls neither stomatiferous nor notably veined, and capsule valves relatively thin and strongly recurved. Both species occur in Chihuahua, Mexico.
The report by R. I. Lonard et al. (1991) that specimens identified as Salix nigra from the lower Rio Grande, Texas, resemble S. humboldtiana in having strongly veined capsules suggests that S. humboldtiana, or intergrades with that species, may occur in Texas. Attempts to locate a voucher specimen were unsuccessful; because strongly veined capsules are diagnostic, further field study is indicated.
An earlier name, Salix chilensis Molina, has been applied to this species; it does not seem to pertain to this taxon (C. K. Schneider 1918).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Hybrids:
Salix fuscescens forms natural hybrids on the arctic coast of Alaska with S. arctica, S. ovalifolia, and S. phlebophylla, and in continental Nunavut with S. herbacea. These hybrids are not usually recognized but they appear sporadically.
Salix fuscescens × S. herbacea has crenate margins and is often confused with the latter species.
Some specimens identified as Salix fuscescens × S. ovalifolia are similar to hybrids with S. phlebophylla, but they lack marcescent leaves.
Salix fuscescens × S. phlebophylla has obovate leaves with one or two pairs of serrulations proximally, and glaucous abaxially as in S. fuscescens, but it grows in relatively dry tundra and has the marcescent, sometimes skeletonized, leaves of S. phlebophylla.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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