Salix humboldtiana
Salix petiolaris
Humboldt's willow
meadow willow, skeleton-leaf willow, slender willow
stipules rudimentary or absent;
petiole shallowly grooved adaxially, 3–11 mm, pubescent, or velvety to glabrescent adaxially;
largest medial blade lorate or very narrowly elliptic, 38–110 × 6–19 mm, 5–9 times as long as wide, base cuneate or convex, margins flat to slightly revolute, entire, serrate, serrulate, or spinulose-serrate, apex acute to acuminate, abaxial surface glaucous, densely long-silky to glabrescent, hairs (white, sometimes also ferruginous), adaxial dull or slightly glossy, glabrous or sparsely pubescent, (hairs white, sometimes also ferruginous);
proximal blade margins sometimes serrulate;
juvenile blade moderately densely long-silky abaxially, hairs white, sometimes also ferruginous.
adaxial nectary square, ovate, or oblong, 0.3–0.7 mm;
filaments distinct, hairy basally;
anthers purple turning yellow, ellipsoid or globose, 0.4–0.6 mm.
adaxial nectary oblong to ovate, 0.3–0.9 mm;
stipe 1.5–4 mm;
ovary pyriform, beak abruptly tapering to styles;
ovules 6–12 per ovary;
styles 0–0.5 mm;
stigmas slenderly to broadly cylindrical, 0.26–0.4–0.8 mm.
5–9 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.
flowering as leaves emerge; staminate stout to globose, 12–29 × 6–17 mm, flowering branchlet 0.8–3 mm; pistillate loosely flowered, stout to globose, 12–39 × 6–18 mm, flowering branchlet 1–11 mm;
floral bract brown, tawny, light rose, or bicolor, 1–2 mm, apex rounded, abaxially sparsely hairy, hairs straight.
= 38.
Salix humboldtiana
Salix petiolaris
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.)
See 107. Salix sericea for a comparative description.
Because reproductive barriers between Salix petiolaris and S. eriocephala are weak, A. Mosseler (1990) suggested that their morphological variability may be due to interspecific gene flow.
Hybrids:
Salix petiolaris forms natural hybrids with S. bebbiana, S. candida, S. eriocephala, S. famelica, S. pellita, and S. sericea. Hybrids with S. alba have been reported (M. L. Fernald 1950) but no convincing specimens have been seen. Controlled pollinations with S. discolor produced no seed (A. Mosseler 1990).
Reports of Salix petiolaris × S. sericea from Massachusetts and Pennsylvania (C. K. Schneider 1921) probably refer to the densely sericeous variant of S. petiolaris. It is sometimes named S. ×subsericea (Andersson) C. K. Schneider but does not seem to be a hybrid (G. W. Argus 1965, 1986; E. G. Voss 1972–1996, vol. 2).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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