Salix humboldtiana |
Salix nivalis |
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Humboldt's willow |
dwarf snow willow, net-leaf willow, snow willow |
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Habit | Plants 0.01–0.04 m, (dwarf, forming clonal mats by rhizomes). | |
Stems | trailing or erect; branches yellow-brown or red-brown, glabrous or pubescent; branchlets yellow-brown or red-brown, glabrous or pilose. |
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Leaves | stipules absent or rudimentary; petiole 1.5–7 mm (sometimes glandular distally or throughout); largest medial blade hypostomatous, (veins impressed-reticulate, 2 pairs of secondary veins arising at or close to base, arcing toward apex,), elliptic to broadly elliptic, 6–22 × 4–15 mm, 1.1–2.8 times as long as wide, base convex, rounded, subcordate, or cuneate, margins slightly revolute, entire (glandular-dotted), apex convex, rounded, or retuse, abaxial surface glabrous or with long-silky hairs, adaxial slightly glossy, glabrous; proximal blade margins entire; juvenile blade glabrous. |
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Staminate flowers | abaxial nectary 0.5–1.3 mm, adaxial nectary narrowly oblong, oblong, or square, 0.5–1.2 mm, nectaries connate and cup-shaped; filaments distinct, glabrous or hairy basally; anthers ellipsoid or shortly cylindrical, 0.4–0.6 mm. |
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Pistillate flowers | abaxial nectary (0–)0.2–0.5 mm, adaxial nectary oblong, 0.2–1 mm, longer than stipe, nectaries distinct or connate and shallowly cup-shaped; stipe 0–0.8 mm; ovary obturbinate, short-silky, hairs flattened, beak abruptly tapering to styles; ovules 8–10 per ovary; styles distinct to connate 1/2 their lengths, 0.2–0.4 mm; stigmas flat, abaxially non-papillate with rounded tip, 0.2–0.26–0.36 mm. |
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Capsules | 3–4 mm. |
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Salix | humboldtiana Willdenow: Humboldt willow is not known to occur in the flora area. |
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It | 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. |
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Catkins | staminate 7–19 × 2.5–6 mm, flowering branchlet 0.5–17 mm; pistillate densely to loosely flowered (4–17 flowers), stout, subglobose or globose, 7–21 × 2–9 mm, flowering branchlet 1–10 mm; floral bract tawny or light rose, 0.8–1.8 mm, apex rounded, entire, abaxially glabrous. |
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2n | = 38. |
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Salix humboldtiana |
Salix nivalis |
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Phenology | Flowering late Jun-late Aug. | |
Habitat | Alpine tundra, cirques, lake basins, rocky slopes and ridges, fellfields | |
Elevation | 1900-4000 m (6200-13100 ft) | |
Distribution |
Mexico to central Chile |
CA; CO; ID; MT; NM; NV; OR; UT; WA; WY; AB; BC
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Discussion | 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.) |
Because geographic overlap is small and evidence of intergradation is tenuous, Salix nivalis is best treated as a species separate from S. reticulata; S. nivalis was previously treated as a subspecies of S. reticulata (G. W. Argus 1986b, 1991). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 34. | FNA vol. 7, p. 66. |
Parent taxa | Salicaceae > Salix > subg. Protitea > sect. Humboldtianae | Salicaceae > Salix > subg. Chamaetia > sect. Chamaetia |
Sibling taxa | ||
Synonyms | S. nivalis var. saximontana, S. reticulata subsp. nivalis, S. reticulata var. saximontana | |
Name authority | Willdenow | Hooker: Fl. Bor.-Amer. 2: 152. (1838) |
Web links |
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